Electrode protection using electrolyte-inhibiting ion conductor

ABSTRACT

The use of ion-conducting materials to protect electrodes is generally described. The ion-conducting material may be in the form of a layer that is adjacent to a polymeric layer, such as a porous separator, to form a composite. At least a portion of the pores of the polymer layer may be filled or unfilled with the ion-conducting material. In some embodiments, the ion-conducting layer is sufficiently bonded to the polymer layer to prevent delamination of the layers during cycling of an electrochemical cell.

TECHNICAL FIELD

The use of ion-conducting materials to protect electrodes is generallydescribed.

BACKGROUND

Rechargeable and primary electrochemical cells oftentimes include one ormore protective layers to protect the electroactive surface. Dependingupon the specific protective layer(s), the protective layer(s) isolatesthe underlying electroactive surface from interactions with theelectrolyte and/or other components within the electrochemical cell. Inorder to provide appropriate protection of the underlying electrode, itis desirable that the protective layer(s) continuously cover theunderlying electrode and exhibit a minimal number of defects. Althoughtechniques for forming protective layer(s) exist, methods that wouldallow formation of protective layer(s) that would improve theperformance of an electrochemical cell would be beneficial.

SUMMARY

Ion-conducting materials used to protect electrodes, and associatedsystems and methods, are generally described. In certain embodiments,the ion-conducting material can inhibit interaction between theprotected electrode and an electrolyte.

The ion-conducting material may be in the form of, according to certainembodiments, a plurality of vias of ion-conducting material at leastpartially surrounded by a separator matrix. In some embodiments, theion-conducting material may be disordered.

In other embodiments, the ion-conducting material may be in the form ofa film positioned adjacent a separator. The ion-conducting material maybe optionally bonded to the separator.

Some embodiments relate to the protection of a lithium-based electrode.The subject matter of the present invention involves, in some cases,interrelated products, alternative solutions to a particular problem,and/or a plurality of different uses of one or more systems and/orarticles.

In certain embodiments, an electrochemical cell is provided. Theelectrochemical cell comprises, in some embodiments, a first electrodecomprising a first electroactive material; a second electrode; and aseparator between the first and second electrodes, comprising pores inwhich electrolyte can reside, and comprising a region proximate thefirst electrode in which the pores are substantially filled with an ionconductor that inhibits interaction of electrolyte with the firstelectroactive material.

In one set of embodiments, an electrochemical cell comprises a firstelectrode comprising an electroactive material, a second electrode, anda composite positioned between the first and second electrodes. Thecomposite comprises a separator comprising pores having an average poresize, wherein the separator has a bulk electronic resistivity of atleast 10⁴ Ohm-meters; and an inorganic ion conductor layer bonded to theseparator, wherein a ratio of a thickness of the inorganic ion conductorlayer to the average pore size of the separator is at least 1.1:1.

In certain embodiments, an electrochemical cell comprises a firstelectrode comprising an electroactive material, a second electrode, anda composite positioned between the first and second electrodes. Thecomposite comprises a separator comprising pores having an average poresize, wherein the separator has a bulk electronic resistivity of atleast 10⁴ Ohm-meters. The composite also includes an inorganic ionconductor layer adjacent to the separator, wherein the inorganic ionconductor layer has a thickness of less than or equal to 1.5 microns.The composite has an air permeation time of at least 20,000 Gurley-saccording to Gurley test TAPPI Standard T 536 om-12.

In certain embodiments, an electrochemical cell comprises a firstelectrode comprising an electroactive material, a second electrode, anda composite positioned between the first and second electrodes. Thecomposite comprises a separator comprising pores having an average poresize, wherein the separator has a bulk electronic resistivity of atleast 10⁴ Ohm meters. The composite also includes an inorganic ionconductor layer bonded to the separator. The inorganic ion conductorlayer is bonded to the separator by covalent bonding and has an ionconductivity of least at least 10⁻⁷ S/cm.

In certain embodiments, a method of forming a component for anelectrochemical cell is provided. The method comprises providing aseparator comprising pores having an average pore size and a surfacehaving a first surface energy, and having a bulk electronic resistivityof at least 10⁴ Ohm meters. The method involves increasing the surfaceenergy of the surface of the separator to a second surface energy in apre-treatment step, wherein the second surface energy is at least 60dynes. The method involves depositing an inorganic ion conductor layeron the surface of the separator. The inorganic ion conductor layer mayhave an ion conductivity of least at least 10⁻⁶ S/cm and a thickness ofless than or equal to 2 microns.

In certain embodiments, a method of forming a component for anelectrochemical involves providing a separator comprising pores havingan average pore size and a surface having a first surface energy, andhaving a bulk electronic resistivity of at least about 10⁴ Ohm meters,subjecting the surface of the separator to a plasma in a pre-treatmentstep, and depositing an inorganic ion conductor layer on the surface ofthe separator. The inorganic ion conductor layer may have an ionconductivity of least at least 10⁻⁶ S/cm and a thickness of less than orequal to 2 microns.

In some embodiments a series of components for an electrochemical cellare provided. In one set of embodiments, a component comprises aseparator comprising pores having an average pore size, and an inorganicion conductor layer bonded to the separator, wherein a ratio of athickness of the inorganic ion conductor layer to the average pore sizeof the separator is at least 1.1:1.

In another set of embodiments, a component comprises a separatorcomprising pores having an average pore size, and an inorganic ionconductor layer bonded to the separator, wherein the inorganic ionconductor layer is bonded to the separator by covalent bonding.

In another set of embodiments, a component comprises a compositecomprising a separator comprising pores having an average pore size,wherein the separator has a bulk electronic resistivity of at least 10⁴Ohm-meters. The composite also includes an inorganic ion conductor layeradjacent to the separator, wherein the inorganic ion conductor layer hasa thickness of less than or equal to 1.5 microns. The composite has anair permeation time of at least 20,000 Gurley-s according to Gurley testTAPPI Standard T 536 om-12.

In another embodiment, the composite comprises a separator between thefirst and second electrodes, comprising pores in which electrolyte canreside, and comprising a region proximate the first electrode in whichthe pores are substantially filled with an ion conductor that inhibitsinteraction of electrolyte with the first electroactive material.

The composites described herein may be configured to or capable of beingarranged between a first electrode and a second electrode of anelectrochemical cell.

Use of a composite described above and herein for separating a firstelectrode and a second electrode of an electrochemical cell (e.g., alithium sulfur cell) and for inhibiting interaction of an electrolytepresent in an electrochemical cell with one of the electrodes of theelectrochemical cell, is also provided.

In some embodiments involving the electrochemical cells described aboveand herein, the ion conductor layer is a part of a multi-layeredstructure comprising more than one ion conductor layers. In someinstances, at least two layers of the multi-layered structure are formedof different materials. In other instances, at least two layers of themulti-layered structure are formed of the same material. The ionconductor layer may be in direct contact with each of the firstelectrode and the separator.

In some embodiments involving the electrochemical cells described aboveand herein, the separator has a thickness between 5 microns and 40microns. The separator may have a bulk electronic resistivity of atleast 10¹⁰ Ohm meters, e.g., between 10¹⁰ Ohm meters and 10¹⁵ Ohmmeters.

In some embodiments involving the electrochemical cells described aboveand herein, the separator is a solid, polymeric separator. In somecases, the separator is a solid comprising a mixture of a polymericbinder and filler comprising a ceramic or a glassy/ceramic material. Incertain embodiments, the separator comprises one or more ofpoly(n-pentene-2), polypropylene, polytetrafluoroethylene, a polyamide(e.g., polyamide (Nylon), poly(ϵ-caprolactam) (Nylon 6),poly(hexamethylene adipamide) (Nylon 66)), a polyimide (e.g.,polynitrile, and poly(pyromellitimide-1,4-diphenyl ether) (Kapton®)(NOMEX®) (KEVLAR®)), polyether ether ketone (PEEK), and combinationsthereof.

In some embodiments involving the electrochemical cells described aboveand herein, the composite is formed by subjecting a surface of theseparator to a plasma prior to depositing the ion conductor layer on thesurface of the separator.

In some embodiments involving the electrochemical cells described aboveand herein, the composite may be a free-standing structure.

In some embodiments involving the electrochemical cells described aboveand herein, the ion conductor layer comprises a glass forming additiveranging from 0 wt % to 30 wt % of the inorganic ion conductor material.

In some embodiments involving the electrochemical cells described aboveand herein, the ion conductor layer comprises one or more lithium salts.A lithium salt may include, for example, LiI, LiBr, LiCl, Li₂CO₃, and/orLi₂SO₄. The one or more lithium salts is added to the inorganic ionconductor material at a range of, e.g., 0 to 50 mol %.

In some embodiments involving the electrochemical cells described aboveand herein, the separator has an average pore size of less than or equalto 5 microns, less than or equal to 1 micron, less than or equal to 0.5microns, between 0.05-5 microns, or between 0.1-0.3 microns.

In some embodiments involving the electrochemical cells described aboveand herein, the ion conductor layer has a thickness of less than orequal to 2 microns, less than or equal to 1.5 microns, less than orequal to 1 micron, less than or equal to 800 nm, less than or equal to600 nm, between 400 nm and 600 nm, or in the range of from 1 nm to 7microns.

In some embodiments involving the electrochemical cells described aboveand herein, the composite has a lithium ion conductivity of at least10⁻⁵ S/cm, at least 10⁻⁴ S/cm, or at least 10⁻³ S/cm at 25 degreesCelsius.

In some embodiments involving the electrochemical cells described aboveand herein, a ratio of a thickness of the ion conductor layer to theaverage pore size of the separator is at least 1.1:1, at least 2:1, atleast 3:1 or at least 5:1.

In some embodiments involving the electrochemical cells described aboveand herein, a strength of adhesion between the separator and the ionconductor layer is at least 350 N/m or at least 500 N/m. In someinstances, a strength of adhesion between the separator and the ionconductor layer passes the tape test according to the standard ASTMD3359-02.

In some embodiments involving the electrochemical cells described aboveand herein, the first electroactive material comprises lithium; e.g.,the first electroactive material may comprise lithium metal and/or alithium alloy. In some cases, the second electrode comprises sulfur as asecond electroactive material.

In some embodiments involving the electrochemical cells described aboveand herein, the ion conductor is deposited onto the separator byelectron beam evaporation or by a sputtering process.

In some embodiments involving the electrochemical cells described aboveand herein, said solid ion conductor is placed against one of said firstand second electrodes. The solid ion conductor may be arranged toinhibit interaction of an electrolyte present in the electrochemicalcell with the electrode against which it is placed.

In some embodiments involving the electrochemical cells described aboveand herein, the solid ion conductor comprises an amorphous lithium-ionconducting oxysulfide, a crystalline lithium-ion conducting oxysulfideor a mixture of an amorphous lithium-ion conducting oxysulfide and acrystalline lithium-ion conducting oxysulfide, e.g., an amorphouslithium oxysulfide, a crystalline lithium oxysulfide, or a mixture of anamorphous lithium oxysulfide and a crystalline lithium oxysulfide.

In some embodiments involving the electrochemical cells described aboveand herein, the present invention relates to the use of a compositeconfigured to or capable of being arranged between a first electrode anda second electrode, the composite comprising a separator, and a solidion conductor contacting and/or bonded to the separator, for separatinga first electrode and a second electrode of an electrochemical cell,e.g., in a lithium sulfur cell. The solid ion conductor may beconfigured and arranged for inhibiting interaction of an electrolytepresent in an electrochemical cell with one of said electrodes of saidelectrochemical cell.

Other advantages and novel features of the present invention will becomeapparent from the following detailed description of various non-limitingembodiments of the invention when considered in conjunction with theaccompanying figures. In cases where the present specification and adocument incorporated by reference include conflicting and/orinconsistent disclosure, the present specification shall control.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting embodiments of the present invention will be described byway of example with reference to the accompanying figures, which areschematic and are not intended to be drawn to scale. In the figures,each identical or nearly identical component illustrated is typicallyrepresented by a single numeral. For purposes of clarity, not everycomponent is labeled in every figure, nor is every component of eachembodiment of the invention shown where illustration is not necessary toallow those of ordinary skill in the art to understand the invention. Inthe figures:

FIGS. 1A and 1B are exemplary schematic illustrations of electrochemicalcells including composite structures comprising an ion conductor layerand a polymer layer (e.g., separator), according to one set ofembodiments.

FIG. 2 is an exemplary schematic illustration of, according to certainembodiments, an example of a disordered structure.

FIG. 3 is an exemplary schematic illustration of, according to someembodiments, a protective structure in which a polymer layer (e.g., apolymer coating, top layer) is deposited over an ion conductor (e.g., aceramic, under the separator layer).

FIG. 4 is an exemplary schematic illustration of, according to someembodiments, a cut-away of the protective structure shown in FIG. 3,showing a portion of the structure after plasma etching has exposed theraised portions of the ion conductor layers.

FIG. 5 is an exemplary schematic illustration of, according to someembodiments, a cut-away of a processed protective structure showing anion conducting layer (e.g., ceramic layer) encased in a non-conductive,polymer coating, deposited on a structure comprising a release layercoated on a carrier substrate

FIG. 6 is an exemplary schematic illustration of, according to someembodiments, of a cut-away of the protective structure after plasmaetching to expose the raised portions of the ion conducting layer (e.g.,a ceramic layer).

FIG. 7 is an exemplary schematic illustration of, according to someembodiments, showing an electroactive material and a currentdistribution layer deposited on the protective structure.

FIG. 8 is an exemplary schematic illustration of, according to someembodiments, of a cut-away of a disordered protective structure showingthe various layers before de-lamination of the carrier substrate.

FIG. 9 is an exemplary schematic illustration of, according to someembodiments, of a free-standing separator film comprising tortuous holepaths.

FIG. 10A is an exemplary schematic illustration of, according to someembodiments, of a porous separator coated with an ion conductor layerand having partially filled pores.

FIG. 10B is an exemplary schematic illustration of, according to someembodiments, of a porous polymer coated with an ion conductor layershowing a current distribution layer on top and having unfilled pores.

FIGS. 11A, 11B, and 11C are exemplary scanning electron microscopy (SEM)images of ceramic coatings deposited on a commercial separator.

FIG. 12 is a plot of air permeation time versus inorganic ion conductorthickness for various inorganic ion conductor-separator composites.

DETAILED DESCRIPTION

Ion-conducting materials used to protect electrodes, and associatedsystems and methods, are generally described.

Layers of ceramic or other inorganic protective materials (e.g.,glasses, glassy-ceramics) have been used to protect electrodes (e.g.,lithium anodes) from adverse interaction with electrolyte materialduring operation of electrochemical cells. For example, protectedlithium anode (PLA) structures have been employed comprising alternatingcontinuous layers of ionically conductive ceramic and ionicallyconductive polymer. In certain cases, such protective electrodestructures can be ineffective. For example, the brittleness of theceramic, defects in the ceramic, and/or the swelling exhibited by thepolymer upon exposure to the electrolyte can cause the protectiveelectrode structure to crack or otherwise fail. The cascade failure ofthese layers can stem from the initial defects in the ceramic, which maybe present from handling and/or from processing. This in turn allows theelectrolyte to seep in and swell the polymer layer. The swelling of thislayer can break the ceramic layers below and the electrolyte penetratesfurther to swell more polymer layers. This can eventually destroy allthe protected layers, which can lead to failure of the electrochemicalcell.

One approach described herein that can be used to address these issuesis using an ion conductor to substantially fills pores within aseparator. The ion conductor can be configured to penetrate from theelectrode (e.g., a lithium layer, or other electrode) to a region inwhich the ion conductor contacts the electrolyte.

Another approach described herein that can be used to address the issuesoutlined above with respect to ineffective electrode protectivestructures involves disposing an ion conductor on the surface of theseparator. In such embodiments, the separator can act as a smoothsubstrate to which a smooth, thin ion conductor layer can be deposited,and the pores may or may not be filled with an ion conductor. Prior todeposition of the ion conductor layer, the surface of the separator maybe treated to enhance its surface energy. The increased surface energyof the separator can allow improved adhesion (e.g., bonding) between theion conductor layer and the separator compared to when the surface ofthe separator is not treated, as described below. As a result ofincreased adhesion between the layers, the likelihood of delamination ofthe layers can be reduced, and the mechanical stability of the ionconductor layer can be improved during cycling of the cell.Additionally, since both the separator and the ion conductor layer canbe included in an electrochemical cell, the ion conductor layer does notneed to be released from a substrate. The avoidance of releasing the ionconductor layer may, in some cases, improve the mechanical integrity ofthe ion conductor layer. In certain embodiments, the resulting ionconductor layer-separator composite can enhance the ion conductorlayer's ability to withstand the mechanical stresses encountered when itis placed in a pressurized cell against a rough cathode. Otheradvantages are described in more detail below.

As used herein, when a layer is referred to as being “on”, “on top of”or “adjacent” another layer, it can be directly on, on top of, oradjacent the layer, or an intervening layer may also be present. A layerthat is “directly on”, “directly adjacent” or “in contact with” anotherlayer means that no intervening layer is present. Likewise, a layer thatis positioned “between” two layers may be directly between the twolayers such that no intervening layer is present, or an interveninglayer may be present.

An approach involving filling all or portions of the pores of theseparator is now described.

In some embodiments, the ion conductor comprises protrusions that extendinto the separator. In some such embodiments, the protrusions can be incontact with an ion conductor material, which can be made of a materialthat is the same as or different from the ion conductor material in theprotrusions. In some embodiments, the ion conductor can be present inthe form of a plurality of discontinuous regions (e.g., in the form ofparticles). In certain embodiments in which the ion conductor is presentin such forms, the loss of function of one ion conducting element doesnot greatly affect the entire structure.

In certain embodiments, the ion conductor regions can be in contact witha separator material (e.g., a polymer separator). The separator materialcan be flexible, in certain embodiments, which can inhibit (and/orprevent) mechanical failure of other adverse mechanical impact (e.g.,plastic deformation) when changes in dimension are introduced to thestructure (e.g., via swelling). The separator material may or may not beionically conductive, which can allow for the use of a wide variety ofseparator materials (e.g., polymers that do or do not swell uponexposure to electrolyte). By adopting designs with such spatialorientations of the ion conductor and the separator, one can, accordingto certain embodiments, remove constraints on the materials that areused, which can allow for the use of already existing materials.

FIGS. 1A and 1B are exemplary cross-sectional schematic illustrations ofelectrochemical cells comprising an ion conductor and a separator,according to one set of embodiments. FIG. 1A shows at least a portion ofthe pores of the separator being filled with an ion conductor, and FIG.1B shows pores of the separator being substantially unfilled by an ionconductor. In FIGS. 1A and 1B, electrochemical cells 100 and 101comprises first electrode 102 and second electrode 104. First electrode102 (and/or second electrode 104) comprises an electroactive material,according to some embodiments. In certain embodiments, the electroactivematerial in first electrode 102 comprises lithium. In some embodiments,first electrode 102 is a negative electrode and second electrode 104 isa positive electrode.

In the exemplary embodiments of FIGS. 1A and 1B, electrochemical cells100 and 101 comprise a separator 106 between first electrode 102 andsecond electrode 104. Separator 106 comprises, in some embodiments,pores 108 in which electrolyte can reside. As shown illustratively inFIG. 1A, separator 106 can comprise, in certain embodiments, regions 110proximate first electrode 102 in which pores 108 are substantiallyfilled with an ion conductor 112. No such filling is shown in the poresof the separator of FIG. 1B.

Ion conductor 112 can inhibit interaction of electrolyte with theelectroactive material within electrode 102. In certain embodiments, ionconductor 112 substantially prevents interaction of electrolyte with theelectroactive material within electrode 102. In some embodiments,inhibiting or preventing the interaction of electrolyte with theelectroactive material within electrode 102 can reduce or eliminate thedegree to which electrode 102 is degraded or otherwise renderedinoperable by the electrolyte. Thus, in this fashion, ion conductor 112can function as a protective structure within the electrochemical cell.

In certain embodiments, the arrangement of ion conductor 112 andseparator 106 may provide one or more advantages over prior electrodeprotective structures. For example, the presence of a plurality of ionconductor structures may provide a plurality of ionic pathways from oneside of the protective structure to the other (i.e., between theprotected electrode and the electrolyte). While ceramic cells or layersmay include pinholes, cracks, and/or grain boundary defects that canpropagate throughout the entire cell or layer, the presence of aplurality of ionic pathways can reduce the impact of a defect in any oneionic pathway. In addition, the positioning of ion conductors within apolymer matrix (e.g., a separator) can decrease the susceptibility ofthe ion conductors to cracking and other failure mechanisms. Thepresence of the polymer matrix can provide flexibility and strength,allowing the composite structure to be more flexible and robust than,for example, a continuous ceramic layer. In addition, because aplurality of ionic pathways through the protective structures arepresent, it is not required that the separator be ionically conductive,which can widen the pool from which separator materials may be selected.

The ion conductor and the separator may be arranged, in certainembodiments, such that the ion conductor extends into the pores of theseparator. In some embodiments, the ion conductor extends, on average,at least about 5%, at least about 10%, at least about 25%, at leastabout 50%, or at least about 80% (and/or, in certain embodiments, up toabout 90% and/or up to substantially 100%) through the pores of theseparator from the side of the separator facing the first electrode,toward the second electrode. Referring to FIG. 1A, for example, ionconductor 112 extends about 50% through the pores of separator 106 fromthe side of separator 106 facing first electrode 102 toward secondelectrode 104. In some embodiments, the ion conductor extends, onaverage, at least about 0.1 microns, at least about 1 micron, or atleast about 2 microns (and/or, in certain embodiments, up to about 10microns, or more) through the pores of the separator from the side ofthe separator facing the first electrode, toward the second electrode.

In certain embodiments, ion conductor material 112 can comprise aplurality of protrusions extending into separator 106. In some suchembodiments, the protrusions can be discrete. In some embodiments, theprotrusions can be connected via an ion conductor material that can bethe same as or different from the ion conductor material from which theion conducting protrusions are formed. For example, referring to FIG.1A, the protrusions of ion conductor material 112 are all connected to abase layer of ion conducting material which is the same as the ionconductor materials used to form the protrusions. In other embodiments,the protrusions of the ion conductor material are connected to a baselayer of ion conducting material which is different from the ionconductor materials used to form the protrusions. In yet otherembodiments, no such base layer is present and the protrusions arephysically isolated from one another.

Protrusions of ion conducting material may be spatially arranged in anysuitable manner. In some embodiments, the protrusions of ion conductingmaterial can be spatially disordered. For example, in FIG. 1A, thelateral distances between the protrusions of ion conductor material 112vary substantially from protrusion to protrusion.

In certain embodiments, the average cross-sectional dimensions of theprotrusions of ion conductor material are dissimilar. For example, inFIG. 2, each of the protrusions of ion conductor material 112 instructure 120 are of different sizes and shapes, leading to asubstantially random spatial distribution of ion conductor material.

In some embodiments, ion conductor 112 can be arranged within the poresof separator 106 by depositing or otherwise forming ion conductor 112over separator 106 such that ion conductor material at least partiallyfills the pores of the separator. While pores 108 in FIGS. 1A and 1B aresubstantially straight, in other embodiments, pores 108 may be tortuous.In some such embodiments, the shadowing and twisted nature of the poreswithin the separator can determine how far into the pores the ionconductor deposition vapor will travel before it contacts a wall andcondenses. In some such embodiments, there will be deeper penetration ofsome vapor, but at a certain point it will grow fast enough to fill thehole, and the partially coated walls deeper than the filled point remainunfilled.

In other embodiments, ion conductor 112 can be arranged within the poresof separator 106 by removing a portion of ion conductor material from alayer of ion conductor material to leave behind protrusions andsubsequently forming separator material over the ion conductor material.

It should be appreciated that while FIGS. 1A and 1B show anelectrochemical cell, in some embodiments not all components shown inthe figure need be present. For instance, the articles and methodsdescribed herein may encompass only components of electrochemical cells(e.g., a separator and an ion conductor without one of an anode and/orcathode). It should also be appreciated that other components that arenot shown in FIGS. 1A and 1B may be included in electrochemical cells insome embodiments. As one example, an ion conductor layer (e.g., aninorganic layer ion conductor layer) may be a part of a multi-layeredstructure comprising more than one ion conductor layers. At least twolayers (e.g., two ion conductor layers) of the multi-layered structuremay be formed of different materials, or the same material. In somecases, at least one of the layers of the multi-layered structure maycomprise a lithium oxysulfide material, as described in more detailbelow. Other configurations are also possible.

An example of a system comprising a protective structure (e.g.,protected lithium anode (PLA)) with a structure (e.g., a disorderedstructure) comprising ionically-conductive materials (e.g., a ceramicvias) surrounded by a separator layer (e.g., a polymer matrix layer) isprovided below. It should be understood that, everywhere in whichlithium is described as an electroactive material, other suitableelectroactive materials (including others described elsewhere herein)could be substituted. In addition, everywhere in which a ceramic isdescribed as the ion conductor, other ion conductor materials (includingothers described elsewhere herein) could be used.

As described herein, previous systems have employed layers of ceramic orother materials (e.g., alternating continuous layers of ceramic andpolymer) to protect lithium anodes from adverse interaction withelectrolyte material during operation of electrochemical cells. Certainstructures having this configuration may be problematic if the ceramiclayer(s) is brittle. To have the ceramic layer function properly as aprotective structure, it should generally remain intact with little orno cracks or defects. Breaks in the continuity of the ceramic layer canallow electrolyte to penetrate, which can create a localized highcurrent path through the ceramic layer. This path can lead to aneventual breakdown in the layers effectiveness as a protector to thelithium metal underneath. Another problem can arise if the electrolytereaches the polymer layer and causes it to swell. Such swelling can berelatively large (e.g., several hundred percent, in some cases).Swelling of the polymer can cause the ceramic layer(s) on either side ofthe polymer to crack, which can, in turn, allow the electrolyte tofurther penetrate the protective structure. In certain cases, a cascadeeffect can be observed as the next polymer layer is exposed to theelectrolyte and swells. This further breaks the ceramic layers until alllayers are compromised and protection of the lithium is compromised.

One way to address the problems discussed above is to develop materialsand/or structures that do not substantially swell or break. This can bechallenging, however. For example, many known polymers, which areionically conductive, swell considerably in various electrochemical cellelectrolytes. Also, it can be difficult to process ceramic materialssuch that they do not contain defects, and handling of such materialswithout introducing defects (e.g., cracks) is difficult.

An alternative involves using a structure which allows the use ofnon-ionically conductive polymers (which are often flexible but have lowswelling in many electrolytes) in combination with a segmented ionconductor (e.g., a ceramic) that inhibits electrolyte interaction withthe electrode. Using a segmented ion conductor can increase thelikelihood that a crack or defect is contained within a small portion ofthe total protective structure. This way, when cracks or other defectsare formed, only a small section of the protective structure is lost,instead of the entire layer. These segments can also allow movementrelative to each other without cracking the whole layer.

Thus the proposed structure change, incorporating these elementsdescribed above, is to build a matrix of ionically conductive ceramic“posts” or “vias” which provide protection for the lithium, yet allowthe ions to pass through. This array of vias can be tied together by apolymer matrix (e.g., a non-ionically conductive polymer matrix), whichcan allow for mechanical flexibility while inhibiting (or eliminating)the amount of swelling upon exposure to the electrolyte. As describedherein, in some embodiments a polymer matrix or polymer layer may be inthe form of a separator (e.g., a commercially-available separator).

The embodiment in FIG. 2 shows structure 120 with an electroactivematerial 102 (e.g., lithium), a polymer layer 106 (e.g., a separator),and an electrode 104, in which ion conductor 112 (e.g., a ceramic) isdeposited in a disordered, porous or columnar form by the depositionprocess. The areas in between can then be filled with polymer to formthe disordered protective structure.

There are different approaches that are possible for the construction ofa protective structure such as a disordered structure PLA. The firstprocess approach involves depositing the ceramic before the polymer isfilled in. This can be done in two configurations. In one configuration,an electroactive material (e.g., lithium) is deposited on a substratecontaining a release layer and a current collector followed by theprotective structure (e.g., PLA construction) on top. This can then bereleased from the carrier substrate. In the second method, the anode isbuilt upside down, with the protective structure being deposited on arelease layer attached to a carrier substrate. The electroactivematerial is then deposited last and the entire structure is released. Inan another method, a release layer is not required and a protectivestructure can be formed directly on a substrate (e.g., a separator orother matrix, such as a polymer matrix) to be included in anelectrochemical cell. For instance, instead of using a carrier substratein the second method, the protective structure may be deposited on aseparator, followed by depositing lithium on the protective structure.

The steps to build a configuration in which the ion conductor (e.g.,ceramic) is deposited before deposition of a polymer can be performed asfollows. As shown in structure 200 in FIG. 3, one can begin with acarrier substrate 205 that has been coated with a release layer 210. Therelease layer can then be metalized with a current collector 215 (e.g.,a copper current collector). In some embodiments, a layer of anelectroactive material 220 (e.g., 25 μm thick lithium) can also bedeposited on top of the current collector, before the addition of an ionconductor material 225 (e.g., a ceramic). The next step comprises usinga plasma system to convert or to deposit while converting with theplasma, a layer of porous or columnar type ion conductor (e.g., 1-2 μmin thickness). The final deposited layer can correspond to a polymerlayer 230 (e.g., a non-swellable, non-conductive polymer layer), whichcan fill at least a portion of (or all of) the area between the ionconductor material columns. This polymer can also completely coat thetop structure as shown in FIG. 3.

For many applications, the polymer-coated structure is not useable inits present form, as the polymer blocks conductivity. To correct this,this entire structure can be placed in front of a plasma etch station toremove the top layer of polymer and ceramic to expose the vias below.This is illustrated in the structure 202 in FIG. 4. In certainembodiments, the entire structure is released from the carriersubstrate. The release layer may be released along with the carrier insome embodiments, but may remain attached to the current collector incertain instances. In such embodiments, the release layer can bepenetrated easily to attach leads to the current collector. As shown inFIG. 4, the top (which can be configured to be exposed to theelectrolyte) has only the tops of the vias as conductors for the current(the discontinuous areas). However the side toward the electroactivematerial includes a single uniform ion conductor layer 225 thatdistributes the current evenly across the electroactive material. Thiscan be desirable, in certain cases, so that during discharge and charge,the stripping and re-plating of the electroactive material is uniform.This layer can crack unlike the multilayer, continuous structure,because as long as it is connected to a via, the entire section willstill function.

The steps to build a configuration in which a protective structure isdeposited on a release layer attached to a carrier substrate can beperformed as follows, as shown illustratively in FIG. 5. In thisconfiguration, a structure 300 is built upside down by depositing onto acarrier substrate 305, a release layer 310, an ion conductor layer 315(e.g., a ceramic), followed by a polymer 320, followed by a lithiumlayer, then releasing the entire structure. The build starts with thecarrier substrate that is coated with the release layer. A porous orcolumnar ion conductor layer (e.g., a ceramic) can be deposited on topof the release layer (e.g., by physical vapor deposition techniques)and, in some cases, modified with a plasma or ion source. The porous orcolumnar ion conductor layer can then be coated with a flexiblenon-conductive, non-swellable polymer as shown in FIG. 5. As in thefirst configuration, a completely coated structure can be plasma etchedto expose the ceramic vias in the polymer matrix (FIG. 6, structure302). As was described in the first configuration, a continuous ionconductor layer 325 (FIG. 7) can be optionally added on top of structure302 of FIG. 6, followed by a current collector (e.g., not shown infigure) and/or an electroactive material layer 330, resulting instructure 304.

The additional ion conductor layer (also referred to herein as a currentdistribution layer (CDL)) can be configured to serve one or more ofseveral functions. First, the CDL can be configured to provide aninterface for the vacuum deposited electroactive material (e.g.,lithium). Second, the CDL can be configured such that it tends to spreadthe electroactive material ion current evenly across its surface. Thiscan eliminate non-uniformities in the current during discharge andcharge where the electroactive material is stripped and re-plated. Incertain cases in which the CDL is not included, the electroactivematerial might re-plate only around the vias leaving voids in the areaswith no ceramic. Lastly, the CDL may be made with a different materialto act as a buffer to overcome any interfacial impedances between theion conductor material and the electroactive material layer. As was alsoobserved before, the CDL can crack but still be effective as long as itis still in contact with a via.

In some embodiments, the carrier substrate can be removed from theprotective structure. The release layer can remain with the substrate orbe attached to the ion conductor layer deposited onto the polymer. Insome cases, the completed structure can be removed from the carriersubstrate. In certain embodiments, the release can be configured todissolve in the electrolyte. In some such embodiments, the release canbe configured to dissolve in the electrolyte without harming the cell.

Another approach to creating a protective structure (e.g., a disorderedPLA structure or other structure) is to start with a porous polymerstructure (e.g., a separator) and following with a deposition of an ionconductor material, such as a ceramic. The deposition of ion conductivematerial may fill at least a portion of the pores of the porous polymerstructure in some embodiments, as shown previously in FIG. 1A. However,as described in more detail herein, in some cases the pores of thepolymer structure are substantially unfilled with a solid ion conductormaterial (e.g., an inorganic ion conductor material), as shownillustratively in FIG. 1B. In some such embodiments, the pores of theseparator may be filled with a liquid (e.g., an ion conductingelectrolyte solvent) in an electrochemical cell.

In certain processes involving starting with a porous polymer structure(e.g., a separator) and then depositing an ion conductor material on topof the polymer structure (regardless of whether or not the pores of thepolymer structure are filled or unfilled with the ion conductor), it maybe desirable to use a porous polymer structure having a smooth surface(i.e., a surface having a low root mean square (RMS) surface roughness).As the smoothness of the layer(s) formed on top of an underlying layermay depend on the smoothness of the underlying layer, the subsequentformation of a protective structure on top of a rough layer may resultin the protective structure having rough surfaces. In some cases, roughsurfaces of the protective structure can lead to defects that allow anelectrolyte or a component of the electrolyte to pass across it duringuse of the electrochemical cell, and may result in a reaction betweenthe electrolyte and/or a component of the electrolyte with anelectroactive layer which the protective layer seeks to protect.

In certain existing methods involving forming a protective layer on topof an electroactive layer, defects may also be formed in the protectivestructure since the deposition of the layer(s) of the structure mayinvolve conditions (e.g., temperature, pressure, and formation rate)that are favorable towards the electroactive layer (e.g., a lowtemperature so as to not cause melting or deformation of theelectroactive layer), but less favorable towards the formation ofdefect-free structures. Additionally, it may be difficult to form asmooth electroactive layer surface on which to deposit the protectivestructure in some embodiments. Defects in the protective layer(s) can beminimized, in some embodiments, by forming a protective structure on asmooth surface of a separator, as described herein. The ability toproduce smooth protective layer(s) may also reduce the thicknessrequirements of the protective layer(s) (while maintaining theprotective layer(s)′ function) to impede electrolyte), leading to anelectrochemical cell having a higher specific energy compared to asimilar cell but having thicker protective layer(s).

An exemplary description of a process which starts with coating a porouspolymer structure (e.g., a separator) is now provided.

In one set of embodiments, the fabrication of structure 400 can bestarted on a carrier substrate 405 which optionally has release coating410 on top, as shown illustratively in FIG. 8. Next, a porous polymercoating 415 can be positioned over the release layer. This type ofporous polymer deposition can naturally result from depositing andcuring certain polymers and/or it could be forced by introducingadditives to the material and/or by disturbing the deposition withplasma or ion beam treatment. In certain embodiments, the holes areconfigured such that they are completely through the polymer. In yetother embodiment, commercially-available polymer layers may be used(e.g., commercially-available separators). Moreover, in certainembodiments, no carrier substrate and/or no release layer is needed, asdescribed in more detail below.

Next, an ion conductor layer 420 such as a ceramic layer can bedeposited over the polymer. For example, vacuum techniques (such ase-beam evaporation, thermal evaporation, or sputtering) may be used todeposit the ion conductor (e.g., ceramic). In some embodiments, ionconductor (e.g., ceramic) may be deposited by drawing a ceramic slurryinto the pores and solidifying (e.g., curing). In certain embodiments,the coating is deposited such that the holes or voids in the polymercoating are filled in with the ion conductor (e.g., ceramic); however,in other embodiments the holes or voids in the polymer coating are notsubstantially filled. In some embodiments, a substantially continuouslayer of ion conductor (e.g., ceramic) is formed over the polymer layer.One may create an ion conductor sheet (e.g., a ceramic sheet) even afterthe holes have been filled for a number of reasons. For example, thesheet can create a layer upon which the lithium will be deposited. Asanother example, the sheet can act to distribute the ionic currentacross the ion conductor (e.g., ceramic) vias which penetrate the porouspolymer layer. In certain embodiments, it is acceptable for the sheet tobreak (while still retaining adequate performance in the electrochemicalcell) as long as the sections remain in contact with the vias. Theionically conductive channels (e.g., a ceramic, the circular structuresconnected to the continuous underlying layer) can be seen extendingthrough the flexible, non-conducting polymer layer.

In certain embodiments, the final deposition step is to coat the ionconductor (e.g., ASL) with an electroactive material 425 (e.g., 25 μm oflithium, or other amounts as described herein). The finished structurecan then be separated from the carrier substrate, in some embodiments,due to the presence of a release layer. The release layer may releasewith the stack, but a layer could be used that releases from thepolymer, so that the release layer remains with the carrier. Thisprocess does not require plasma etching. Since plasma etching can betime consuming, elimination of such steps can be preferred to save time.

One variant of the above is to use a free-standing, porous, polymerlayer as the polymer matrix (e.g., a free-standing separator). In somesuch cases, no release coating or carrier substrate is required.According to one exemplary fabrication process, a porous, polymer layer500 is provided, as illustrated in FIG. 9. The porous polymer layer maybe conductive or non-conductive to ions. One example of a suitable filmis a commercially available porous, polymer layer, such as those used inbattery separators (and including those described elsewhere herein).This film can be used as an as-cast polymer matrix. The hole pathwaysthrough the film can be quite tortuous in some embodiments. In certainembodiments, the hole pathways through the film pass completely throughthe film. This free standing film can then be coated with an ionconductor (e.g., a ceramic).

The approach of coating a free-standing polymer layer (e.g., aseparator) with an ion conductor material offers a number of advantagesover method of fabricating other protective structures. First amongthese is the fact that the resulting structure does not have to bereleased from a carrier substrate. This not only results in a costsavings and a reduction of materials, but it avoids the possibility ofdamaging the fragile ion conductor coating during the release step.Second, binding the ion conductor material to the surface of theseparator creates a mechanically stable platform for the thin ionconductor (e.g., ceramic) coatings, greatly enhancing the coating'sability to withstand the mechanical stresses encountered when it isplaced in a pressurized cell against a rough cathode. Third, such aprocess can be accomplished in a single chamber pump down. Not having toopen the vacuum chamber during the deposition process reduces thechances for contamination as well as minimizes the handling of thematerial.

As described herein, in some embodiments an ion conductor material canbe deposited onto a polymer layer, such as a separator, using a vacuumdeposition process (e.g., sputtering, CVD, thermal or E-beamevaporation). Vacuum deposition can permit the deposition of smooth,dense, and homogenous thin layers. In some embodiments it is desirableto deposit thin layers of an inorganic ion conductor material sincethick layers can increase the internal resistance of the battery,lowering the battery rate capability and energy density. As shownillustratively in structure 502 in FIG. 10A, the pores of a polymerlayer 500 (e.g., a separator) can be partially filled with an ionconductor 505 (e.g., ceramic), which may be conductive to ions of anelectroactive material (e.g., lithium). However, in other embodiments,the pores of the polymer layer are substantially unfilled with the ionconductor, as illustrated in FIG. 10B. In embodiments in which all orportions of the pores of the polymer layer are not filled with aninorganic ion conductor (e.g., a ceramic), those portions may be filledwith an electrolyte solvent when positioned in an electrochemical cell.In some embodiments, the ion conductor may be coated with a final layerof an electroactive material 510 (e.g., lithium).

The ion conductor layer may be continuous in some embodiments, ordiscontinuous in other embodiments. In embodiments in which the pores ofthe polymer layer are at least partially filled with ion conductor, theion conductor layer can flex and crack with no harm done to thestructure's functionality as long as the broken sections are stillattached to the vias. In embodiments in which the pores of the polymerlayer are substantially unfilled with ion conductor, the ion conductorlayer can still function in the presence of cracks as long as theunfilled side of the pores are in the electrolyte (e.g., electrolytesolvent). In some such embodiments, the connection of the ionicconductor to the electrolyte will allow the cell to function.

To form an electrode, an electroactive material such as lithium may bedeposited on the polymer layer-ion conductor composite. In FIG. 10A, thefinal form of the protective structure is illustrated with lithiumdeposited on the ion conductor-coated polymer layer with partiallyfilled pores. In FIG. 10B, the final form of the protective structure isillustrated with lithium deposited on the ceramic coated polymer layerwith no pore filling. The lithium can be configured to adhere to the ionconductive layer, as described in more detail below. In certainembodiments of this process, there is no etching involved, which canmake the process very fast and efficient.

It should also be appreciated that although several figures shown hereinillustrate a single ion conductor layer, in some embodiments aprotective structure includes multiple ion conductor layers (e.g., atleast 2, 3, 4, 5, or 6 ion conductor layers) to form a multi-layeredstructure. As one example, an ion conductor layer (e.g., an inorganiclayer ion conductor layer) may be a part of a multi-layered structurecomprising more than one ion conductor layers, wherein at least twolayers (e.g., two ion conductor layers) of the multi-layered structureare formed of different materials. In other instances, at least twolayers of the multi-layered structure (e.g., two ion conductor layers)are formed of the same material. In some cases, at least one of thelayers of the multi-layered structure may comprise a lithium oxysulfidematerial. The multi-layered structure may optionally include polymerlayers (e.g., at least 1, 2, 3, 4, 5, or 6 polymer layers). In someembodiments, the polymer layers are interspersed between two or more ionconductor layers. Each of the layers of the multi-layered structure mayindependently have features (e.g., thickness, conductivity, bulkelectronic resistivity) described generally herein for the ion conductorlayer and/or polymer layer.

In structures involving a single ion conductor layer, the ion conductorlayer (which may comprise a lithium oxysulfide in some embodiments) maybe in direct contact with each an electroactive material of a firstelectrode and the separator/polymer layer.

As described herein, in some embodiments involving the formation of aprotective structure by disposing an ion conductor on the surface of apolymer layer (e.g., a separator), such as in some of the embodimentsdescribed with respect to FIGS. 1-11, it is desirable to increase thebonding or adhesive strength between the ion conductor and the polymerlayer. As a result of increased adhesion between the layers, thelikelihood of delamination of the layers can be reduced and themechanical stability of the ion conductor layer can be improved duringcycling of the cell. For example, the resulting ion conductorlayer-polymer composite can enhance the ion conductor layer's ability towithstand the mechanical stresses encountered when it is placed in apressurized cell against a rough cathode. Accordingly, in someembodiments, prior to deposition of the ion conductor layer, the surfaceof the polymer layer (e.g., separator) may be treated (e.g., in apre-treatment process) to enhance the surface energy of the polymerlayer. The increased surface energy of the polymer layer (e.g.,separator) can allow improved adhesion between the ion conductor layerand the separator compared to when the surface of the separator is nottreated.

In certain embodiments, adhesion is enhanced when a ratio of thethickness of the ion conductor layer to the average pore diameter of thepolymer layer (e.g., separator) is present in certain ranges, asdescribed in more detail below.

To increase the surface energy of the polymer layer (i.e., activate thesurface of the polymer layer), a variety of methods may be used. Themethod may involve, for example, a pre-treatment step in which thesurface of the polymer layer (e.g., separator) is treated prior todeposition of an ion conductor material. In certain embodiments,activation or a pre-treatment step involves subjecting the polymer layer(e.g., separator) to a source of plasma. For example, an anode layer ionsource (ALS) may be used to generate a plasma. In general, an anodelayer ion source involves generating electrons by an applied potentialin the presence of a working gas. The resulting plasma generated createsadditional ions and electrons, which accelerate towards the targetsubstrate (e.g., the polymer layer), providing ion bombardment of asubstrate. This bombardment of the polymer layer substrate increases thesurface energy of the polymer layer and promotes adhesion between theseparator and the ion conductor material to follow.

Various working gases can be used during a surface activation processsuch as plasma treatment. In general, surface activation may occur inthe presence of one or more gases including: air, oxygen, ozone, carbondioxide, carbonyl sulfide, sulfur dioxide, nitrous oxide, nitric oxide,nitrogen dioxide, nitrogen, ammonia, hydrogen, freons (e.g., CF₄,CF₂Cl₂, CF₃Cl), silanes (e.g., SiH₄, SiH₂(CH₃)₂, SiH₃CH₃), and/or argon.

In general, plasma treatment modifies the surface of the polymer layer(e.g., the separator) by ionizing the working gas and/or surface and, insome instances, forming or depositing activated functional chemicalgroups onto the surface. In certain embodiments, activation of certainfunctional groups on the surface of the polymer layer may promotebinding between the polymer layer and an ion conductor material. Incertain embodiments, the activated functional groups may include one ormore of the following: carboxylates (e.g., —COOH), thiols (e.g., —SH),alcohols (e.g., —OH), acyls (e.g., —CO), sulfonics and/or sulfonic acids(e.g., —SOOH or —SO₃H), amines (e.g., —NH₂), nitric oxides (e.g., —NO),nitrogen dioxides (e.g., —NO₂), chlorides (e.g., —Cl), haloalkyl groups(e.g., CF₃), silanes (e.g., SiH₃), and/or organosilanes (SiH₂CH₃). Otherfunctional groups are also possible.

In certain embodiments, plasma treatment, such as an ALS process, isperformed in a chamber at a pressure ranging between, for example, 10⁻²to 10⁻⁸ Torr. For instance, the pressure may be greater than or equal to10⁻⁸ Torr, greater than or equal to 10⁻⁷ Torr, greater than or equal to10⁻⁶ Torr, greater than or equal to 10⁻⁵ Torr, greater than or equal to10⁻⁴ Torr, or greater than or equal to 10⁻³ Torr. The pressure may beless than or equal to 10⁻² Torr, less than or equal to 10⁻³ Torr, lessthan or equal to 10⁻⁴ Torr, less than or equal to 10⁻⁵ Torr, or lessthan or equal to 10⁻⁶ Torr. Combinations of the above-referenced rangesare also possible.

Plasma treatment may generally be performed with a power of the ionsource ranging between, for example, 5 W to 200 W. For instance, thepower may be greater than or equal to 5 W, great than or equal to 10 W,greater than or equal to 20 W, greater than or equal to 50 W, greaterthan or equal to 100 W, or greater than or equal to 200 W. The power maybe less than or equal to 200 W, or less than or equal to 100 W, or lessthan or equal to 50 W, or less than or equal to 20 W, or less than orequal to 5 W. Combinations of the above-referenced power ranges are alsopossible.

Actual surface energy enhancement is a function of pressure, power, andexposure time, with care taken not to overexpose the material which canlead to thermal damage. For example, the exposure time (i.e., the timefor which the polymer layer is subjected to plasma treatment) may begreater than or equal to 1 second, greater than or equal to 10 seconds,greater than or equal to 30 seconds, greater than or equal to 1 minute,greater than or equal to 2 minutes, greater than or equal to 5 minutes,greater than or equal to 10 minutes, greater than or equal to 20minutes, greater than or equal to 30 minutes, greater than or equal to 1hour, or greater than or equal to 5 hours. The exposure time may be lessthan or equal to 10 hours, less than or equal to 1 hour, less than orequal to 30 minutes, less than or equal to 10 minutes, less than orequal to 5 minutes, less than or equal to 1 minute, less than or equalto 10 seconds, or less than or equal to 1 second. Combinations of theabove-referenced exposure times are also possible.

It would be appreciable to those skilled in the art that setupconditions can vary depending on the efficiency of the plasma system,the efficiency of the power supply, RF matching issues, gas distributionand selection, distance from target substrate, time of plasma exposure,etc. Thus, various combinations of power at which the plasma source isoperated, the operating pressure, gas selection, and the length of timeof exposure to the plasma source are possible.

Although plasma treatment is primarily described for increasing thesurface energy of a substrate (e.g., a polymer layer such as aseparator), other methods for increasing the surface energy of asubstrate are also possible. For example, in certain embodiments, flamesurface treatment, corona treatment, chemical treatment, surfaceoxidation, absorption of functional groups to the surface, and/orsurface grafting may be used to increase the surface energy of asubstrate.

The surface energy of the polymer layer (e.g., separator) can beincreased to any suitable value. In some embodiments, the surface energyof the polymer layer (e.g., separator) before treatment may be, forexample, between 0 and 50 dynes. For example, the surface energy may beat least 0 dynes, at least 10 dynes, at least 20 dynes, at least 30dynes, at least 40 dynes, or at least 50 dynes. The surface energy maybe less than 50 dynes, less than 40 dynes, less than 30 dynes, less than20 dynes, or less than 10 dynes. Combinations of the above-referencedranges are also possible.

In some embodiments, the surface energy of the polymer layer (e.g.,separator) after treatment may range from, for example, between 30 dynesand 100 dynes (1 dyne=1 g·cm/s²=10⁻⁵ kg·m/s²=10⁻⁵ N). In certainembodiments, the surface energy of the polymer layer after treatment maybe at least 30 dynes, at least 40 dynes, at least 50 dynes, at least 60dynes, at least 70 dynes, at least 80 dynes, at least 90 dynes. Thesurface energy after treatment may be, for example, less than 100 dynes,less than 90 dynes, less than 80 dynes, less than 70 dynes, less than 60dynes, or less than 50 dynes. Combinations of the above-referencedranges are also possible. Other surface energies are also possible.

In certain embodiments, the surface energy of a polymer surface beforetreatment can be increased at least 1.2 times, at least 1.5 times, atleast 2 times, at least 3 times, at least 5 times, at least 10 times, atleast 20 times, at least 50 times, at least 70 times, at least 100 timesafter treatment. In some cases, the surface treatment may be increasedup to 500 times after treatment. Other increases in surface energy arealso possible.

As described herein, in some embodiments treatment of a surface resultsin chemical and/or physical bonds between an ion conductor and a polymerlayer (e.g., a separator) being formed. In some embodiments, the bondsmay include covalent bonds. Additionally or alternatively, non-covalentinteractions (e.g., hydrophobic and/or hydrophilic interactions,electrostatic interactions, van der Waals interactions) may be formed.Generally, treatment (e.g., pre-treatment) of a surface resulting inbond formation increases the degree of adhesion between two layerscompared to the absence of such treatment.

To determine relative adhesion strength between two layers, a tape testcan be performed. Briefly, the tape test utilizes pressure-sensitivetape to qualitatively asses the adhesion between a first layer (e.g., apolymer layer) and a second layer (e.g., a ion conducting layer). Insuch a test, an X-cut can be made through the first layer (e.g., polymerlayer/separator) to the second layer (e.g., ion conducting layer).Pressure-sensitive tape can be applied over the cut area and removed. Ifthe polymer layer stays on the ion conducting layer, adhesion is good.If the polymer layer comes off with the strip of tape, adhesion is poor.The tape test may be performed according to the standard ASTM D3359-02.In some embodiments, a strength of adhesion between the separator andthe inorganic ion conductor layer passes the tape test according to thestandard ASTM D3359-02, meaning the ion conductor layer does notdelaminate from the polymer layer during the test. In some embodiments,the tape test is performed after the two layers (e.g., a first layersuch as a polymer layer/separator, to a second layer such as an ionconducting layer) have been included in a cell, such as a lithium-sulfurcell or any other appropriate cell described herein, that has beencycled at least 5 times, at least 10 times, at least 15 times, at least20 times, at least 50 times, or at least 100 times, and the two layerspass the tape test after being removed from the cell (e.g., the firstlayer does not delaminate from the second layer during the test).

The peel test may include measuring the adhesiveness or force requiredto remove a first layer (e.g., a polymer layer) from a unit area of asurface of a second layer (e.g., a ion conducting layer), which can bemeasured in N/m, using a tensile testing apparatus or another suitableapparatus. Such experiments can optionally be performed in the presenceof a solvent (e.g., an electrolyte) or other components to determine theinfluence of the solvent and/or components on adhesion.

In some embodiments, the strength of adhesion between two layers (e.g.,a first layer such as a polymer layer and a second layer such as an ionconductor layer) may be increased as a result of a treatment (e.g.,pre-treatment) step described herein. The strength of adhesion aftertreatment may range, for example, between 100 N/m to 2000 N/m. Incertain embodiments, the strength of adhesion may be at least 50 N/m, atleast 100 N/m, at least 200 N/m, at least 350 N/m, at least 500 N/m, atleast 700 N/m, at least 900 N/m, at least 1000 N/m, at least 1200 N/m,at least 1400 N/m, at least 1600 N/m, or at least 1800 N/m. In certainembodiments, the strength of adhesion may be less than or equal to 2000N/m, less than or equal to 1500 N/m, less than or equal to 1000 N/m,less than or equal to 900 N/m, less than or equal to 700 N/m, less thanor equal to 500 N/m, less than or equal to 350 N/m, less than or equalto 200 N/m, less than or equal to 100 N/m, or less than or equal to 50N/m. Other strengths of adhesion are also possible.

As described herein, the relative thickness of the ion conductor layerto the average pore diameter of the polymer layer (e.g., separator) mayinfluence the degree of adhesive strength or bonding between the twolayers in a composite. For instance, in some cases the thickness of theion conductor layer may be greater than the average pore diameter (orlargest pore diameter) of polymer layer (e.g., separator), which resultsin the formation of a smooth, dense, and homogenous ion conductor layerthat resists delamination from polymer layer.

As described herein, in an electrochemical cell, the ion conductor layermay serve as a solvent barrier which acts to prevent or reduce thelikelihood of a liquid electrolyte from interacting with anelectroactive material (e.g., lithium metal). In some embodiments, theability of the composite ion conductor layer-polymer layer (e.g.,separator layer) to act as a barrier can be measured in part by an airpermeation test (e.g., the Gurley Test). The Gurley Test determines thetime required for a specific volume of air to flow through a standardarea of the material. As such, larger air permeation times (Gurley-sec)generally correspond to better barrier properties.

One of ordinary skill in the art may have expected that improved barrierproperties (e.g., higher air permeation times) would be achieved byusing relatively thicker inorganic ion conductor layers, since thickerlayers may be more difficult for fluids to penetrate across the layer.However, as described in more detail below, the inventors observed thata reduced thickness of the ion conductor layer in an inorganic ionconductor layer-separator composite resulted in an improvement inbarrier properties, as measured by an increase in air permeation timeusing the Gurley Test, compared to inorganic ion conductorlayer-separator composites having relatively thicker inorganic ionconductor layers (see Example 3 and FIG. 12). Additionally, thecombination of a thin inorganic ion conductor layer and a plasma treatedseparator showed the highest air permeation time (and, therefore,enhanced barrier properties), compared to composites that did notinclude a plasma treated separator, or a composite that had a relativelythicker inorganic ion conductor layer. Without wishing to be bound byany theory, the inventors believe that high permeation times, andtherefore good barrier properties, are contributed by good strength ofadhesion between the two layers and good mechanical flexibility (i.e.,lower film stresses) of the ion conductor layer so as to reduce thelikelihood of cracking of the layer. Cracking of the ion conductorlayer, similar to delamination between layers, typically results inpoorer barrier properties.

In some embodiments, air permeation times of a composite describedherein (e.g., an ion conductor layer-polymer layer/separator layercomposite) may be at least 1,000 Gurley sec, at least 5,000 Gurley-s, atleast 10,000 Gurley-s, at least 20,000 Gurley-s, at least 40,000Gurley-s, at least 60,000 Gurley-s, at least 80,000 Gurley-s, at least100,000 Gurley-s, at least 120,000 Gurley-s, at least 140,000 Gurley-s,at least 160,000 Gurley-s, at least 180,000 Gurley-s, at least 200,000Gurley-s, at least 500,000 Gurley-s, or at least 10⁶ Gurley-s. In someembodiments, the composite is substantially impermeable. In someembodiments, the air permeation time may be less than or equal to 10⁶Gurley-s, less than or equal to 500,000 Gurley-s, less than or equal to200,000 Gurley-s, less than or equal to 150,000 Gurley-s, less than orequal to 120,000 Gurley-s, less than or equal to 80,000 Gurley-s, lessthan or equal to 40,000 Gurley-s, less than or equal to 20,000 Gurley-s,less than or equal to 10,000 Gurley-s, or less than or equal to 5,000Gurley-s. The air permeation times and Gurley tests described hereinrefer to those performed according to TAPPI Standard T 536 om-12, whichinvolves a pressure differential of 3 kPa and a sample size of a squareinch.

An ion conductor or ion conductor layer described herein can be formedof a variety of types of materials. In certain embodiments, the materialfrom which the ion conductor is formed may be selected to allow ions(e.g., electrochemically active ions, such as lithium ions) to passthrough the ion conductor but to substantially impede electrons frompassing across the ion conductor. By “substantially impedes”, in thiscontext, it is meant that in this embodiment the material allows lithiumion flux at least ten times greater than electron passage.

In some embodiments, the material used for an ion conductor layer has ahigh enough conductivity (e.g., at least 10⁻⁶ S/cm, or anotherconductivity value described herein) in its first amorphous state. Thematerial may also be chosen for its ability to form a smooth, dense andhomogenous thin films, especially on a polymer layer such as aseparator. Lithium oxysulfides may especially include thesecharacteristics.

The ion conductor can be configured to be substantially electronicallynon-conductive, in certain embodiments, which can inhibit the degree towhich the ion conductor causes short circuiting of the electrochemicalcell. In certain embodiments, all or part of the ion conductor can beformed of a material with a bulk electronic resistivity of at leastabout 10⁴ Ohm-meters, at least about 10⁵ Ohm-meters, at least about 10¹⁰Ohm-meters, at least about 10¹⁵ Ohm-meters, or at least about 10²⁰Ohm-meters. The bulk electronic resistivity may be, in some embodiments,less than or equal to about 10²⁰ Ohm-meters, or less than or equal toabout 10¹⁵ Ohm-meters. Combinations of the above-referenced ranges arealso possible. Other values of bulk electronic resistivity are alsopossible.

In some embodiments, the average ionic conductivity (e.g., lithium ionconductivity) of the ion conductor material is at least about 10⁻⁷ S/cm,at least about 10⁻⁶ S/cm, at least about 10⁻⁵ S/cm, at least about 10⁻⁴S/cm, at least about 10⁻³ S/cm, at least about 10⁻² S/cm, at least about10⁻¹ S/cm, at least about 1 S/cm, or at least about 10 S/cm. The averageionic conductivity may less than or equal to about 20 S/cm, less than orequal to about 10 S/cm, or less than or equal to 1 S/cm. Conductivitymay be measured at room temperature (e.g., 25 degrees Celsius).

In some embodiments, the ion conductor can be a solid. In someembodiments, the ion conductor comprises or may be substantially formedof a non-polymeric material. For example, the ion conductor may compriseor may be substantially formed of an inorganic material.

Although a variety of materials can be used as an ion conductive layer,in one set of embodiments, the ion conductor layer is an inorganic ionconductive layer. For example, the inorganic ion conductor layer may bea ceramic, a glass, or a glassy-ceramic. Suitable glasses include, butare not limited to, those that may be characterized as containing a“modifier” portion and a “network” portion, as known in the art. Themodifier may include a metal oxide of the metal ion conductive in theglass. The network portion may include a metal chalcogenide such as, forexample, a metal oxide or sulfide. Ion conductors may include a glassymaterial selected from one or more of lithium nitrides, lithiumsilicates, lithium borates, lithium aluminates, lithium phosphates,lithium phosphorus oxynitrides, lithium silicosulfides, lithiumgermanosulfides, lithium oxides (e.g., Li₂O, LiO, LiO₂, LiRO₂, where Ris a rare earth metal), lithium lanthanum oxides, lithium titaniumoxides, lithium borosulfides, lithium aluminosulfides, and lithiumphosphosulfides, and combinations thereof. In some embodiments, the ionconductor comprises an oxysulfide such as lithium oxysulfide. In oneembodiment, the ion conductor comprises a lithium phosphorus oxynitridein the form of an electrolyte.

In certain embodiments in which an inorganic ion conductor materialdescribed herein comprises a lithium oxysulfide, the lithium oxysulfide(or an ion conductor layer comprising a lithium oxysulfide) may have anoxide content between 0.1-20 wt %. The oxide content may be measuredwith respect to the total weight of the lithium oxysulfide material orthe total weight of the ion conductor layer that comprises the lithiumoxysulfide material. For instance, the oxide content may be at least 0.1wt %, at least 1 wt %, at least 2 wt %, at least 5 wt %, at least 10 wt%, %, at least 15 wt %, or at least 20 wt %. In some embodiments, theoxide content may be less than or equal to 20 wt %, less than or equalto 15 wt %, less than or equal to 10 wt %, less than or equal to 5 wt %,less than or equal to 2 wt %, or less than or equal to 1 wt % of thelithium oxysulfide. Combinations of the above-noted ranges are alsopossible. The elemental composition, including oxide content, of a layermay be determined by methods such as energy-dispersive X-rayspectroscopy.

In some embodiments in which an inorganic ion conductor materialdescribed herein comprises a lithium oxysulfide, the lithium oxysulfidematerial (or an ion conductor layer comprising a lithium oxysulfide) hasan atomic ratio of sulfur atoms to oxygen atoms (S:O) of between, forexample, 0.5:1 to 1000:1. For instance, the atomic ratio between sulfuratoms to: oxygen atoms (S:O) in the lithium oxysulfide material (or anion conductor layer comprising a lithium oxysulfide) may be at least0.5:1, at least 0.667:1, at least 1:1, at least 2:1, at least 3:1, atleast 4:1, at least 5:1, at least 10:1, at least 20:1, at least 50:1, atleast 70:1, at least 90:1, at least 100:1, at least 200:1, at least500:1, or at least 1000:1. The atomic ratio of sulfur atoms to oxygenatoms (S:O) in the lithium oxysulfide material (or an ion conductorlayer comprising a lithium oxysulfide) may be less than or equal to1000:1, less than or equal to 500:1, less than or equal to 200:1, lessthan or equal to 100:1, less than or equal to 90:1, less than or equalto 70:1, less than or equal to 50:1, less than or equal to 20:1, lessthan or equal to 10:1, less than or equal to 5:1, less than or equal to3:1, or less than or equal to 2:1. Combinations of the above-notedranges are also possible (e.g., an atomic ratio of S:O of between 0.67:1to 1000:1, or between 4:1 to 100:1). Other ranges are also possible. Theelemental composition of a layer may be determined by methods such asenergy-dispersive X-ray spectroscopy.

In some embodiments, a lithium oxysulfide material described herein mayhave a formula of x(yLi₂S+zLi₂O)+MS₂ (where M is Si, Ge, or Sn), wherey+z=1, and where x may range from 0.5-3. In certain embodiments, x is atleast 0.5, at least 1.0, at least 1.5, at least 2.0, or at least 2.5. Inother embodiments, x is less than or equal to 3.0, less than or equal to2.5, less than or equal to 2.0, less than or equal to 1.5, less than orequal to 1.0, or less than or equal to 0.5. Combinations of theabove-noted ranges are also possible. Other values for x are alsopossible.

The ion conductor may comprise, in some embodiments, an amorphouslithium-ion conducting oxysulfide, a crystalline lithium-ion conductingoxysulfide or a mixture of an amorphous lithium-ion conductingoxysulfide and a crystalline lithium-ion conducting oxysulfide, e.g., anamorphous lithium oxysulfide, a crystalline lithium oxysulfide, or amixture of an amorphous lithium oxysulfide and a crystalline lithiumoxysulfide.

In some embodiments, the inorganic ion conductor, such as a lithiumoxysulfide described above, comprises a glass forming additive rangingfrom 0 wt % to 30 wt % of the inorganic ion conductor material. Examplesof glass forming additives include, for example, SiO₂, Li₂SiO₃, Li₄SiO₄,Li₃PO₄, LiPO₃, Li₃PS₄, LiPS₃, B₂O₃, B₂S₃. Other glass forming additivesare also possible. In certain embodiments, glass forming additives maybe at least 5 wt %, at least 10 wt %, at least 15 wt %, at least 20 wt%, at least 25 wt %, or at least 30 wt % of the inorganic ion conductormaterial. In certain embodiments, glass forming additives may be lessthan or equal to 30 wt %, less than or equal to 25 wt %, less than orequal to 20 wt %, less than or equal to 15 wt %, or less than or equalto 10 wt % of the inorganic ion conductor material. Combinations of theabove-noted ranges are also possible. Other values of glass formingadditives are also possible.

In some embodiments, one or more additional salts (e.g., lithium saltssuch as LiI, LiBr, LiCl, Li₂CO₃, or Li₂SO₄) may be added to theinorganic ion conductor material at a range of, e.g., 0 to 50 mol %.Other salts are also possible. In certain embodiments, additional saltsare at least 0 mol %, at least 10 mol %, at least 20 mol %, at least 30mol %, at least 40 mol %, or at least 50 mol %. In certain embodiments,additional salts are less than or equal to 50 mol %, less than or equalto 40 mol %, less than or equal to 30 mol %, less than or equal to 20mol %, or less than or equal to 10 mol %. Combinations of theabove-noted ranges are also possible. Other values of mol % are alsopossible.

Additional examples of ion conductors include lithium nitrides, lithiumsilicates, lithium borates, lithium aluminates, lithium phosphates,lithium phosphorus oxynitrides, lithium silicosulfides, lithiumgermanosulfides, lithium oxides (e.g., Li₂O, LiO, LiO₂, LiRO₂, where Ris a rare earth metal), lithium lanthanum oxides, lithium titaniumoxides, lithium borosulfides, lithium aluminosulfides, and lithiumphosphosulfides, and combinations thereof.

In certain embodiments, the ion conductor is formed of a single-ionconductive material (e.g., a single-ion conductive ceramic material).

Other suitable materials that could be used to form all or part of theion conductor include the ionically conductive materials described inU.S. Patent Publication No. 2010/0327811, filed Jul. 1, 2010 andpublished Dec. 30, 2010, entitled “Electrode Protection in Both Aqueousand Non-Aqueous Electromechanical Cells, Including Rechargeable LithiumBatteries,” which is incorporated herein by reference in its entiretyfor all purposes.

Those of ordinary skill in the art, given the present disclosure, wouldbe capable of selecting appropriate materials for use as the ionconductor. Relevant factors that might be considered when making suchselections include the ionic conductivity of the ion conductor material;the ability to deposit, etch, or otherwise form the ion conductormaterial on or with other materials in the electrochemical cell; thebrittleness of the ion conductor material; the compatibility of the ionconductor material with the polymer or separator material; thecompatibility of the ion conductor material with the electrolyte of theelectrochemical cell; the ion conductivity of the material (e.g.,lithium ion conductivity); and/or the ability to adhere the ionconductor to the separator material.

The ion conductor material may be deposited by any suitable method suchas sputtering, electron beam evaporation, vacuum thermal evaporation,laser ablation, chemical vapor deposition (CVD), thermal evaporation,plasma enhanced chemical vacuum deposition (PECVD), laser enhancedchemical vapor deposition, and jet vapor deposition. The technique usedmay depend on the type of material being deposited, the thickness of thelayer, etc. In certain embodiments, at least a portion of the ionconductor material may be etched or otherwise removed, after which aseparator material (e.g., a polymeric separator material) may be formedover the ion conductor material.

As described herein, in certain preferred embodiments, an ion conductormaterial can be deposited onto a separator using a vacuum depositionprocess (e.g., sputtering, CVD, thermal or E-beam evaporation). Vacuumdeposition can permit the deposition of smooth, dense, and homogenousthin layers. In other embodiments, the ion conductor (e.g., ceramic) canbe coated by drawing and casting the ion conductor from a slurry or gel.

In embodiments in which the ion conductor is in the form of a layer(e.g., a layer adjacent and/or attached to a polymer layer (e.g., aseparator)), the thickness of the ion conductor layer may vary. Thethickness of an ion conductor layer may vary over a range from, forexample, 1 nm to 7 microns. For instance, the thickness of the ionconductor layer may be between 1-10 nm, between 10-100 nm, between 10-50nm, between 30-70 nm, between 100-1000 nm, or between 1-7 microns. Thethickness of an ion conductor layer may, for example, be less than orequal to 7 microns, less than or equal to 5 microns, less than or equalto 2 microns, less than or equal to 1000 nm, less than or equal to 600nm, less than or equal to 500 nm, less than or equal to 250 nm, lessthan or equal to 100 nm, less than or equal to 70 nm, less than or equalto 50 nm, less than or equal to 25 nm, or less than or equal to 10 nm.In some embodiments, an ion conductor layer is at least 10 nm thick, atleast 20 nm thick, at least 30 nm thick, at least 100 nm thick, at least400 nm thick, at least 1 micron thick, at least 2.5 microns thick, or atleast 5 microns thick. Other thicknesses are also possible. Combinationsof the above-noted ranges are also possible.

As described herein, the methods and articles provided herein may allowthe formation of smooth surfaces. In some embodiments, the RMS surfaceroughness of an ion conductor layer of a protective structure may be,for example, less than 1 μm. In certain embodiments, the RMS surfaceroughness for such surfaces may be, for example, between 0.5 nm and 1 μm(e.g., between 0.5 nm and 10 nm, between 10 nm and 50 nm, between 10 nmand 100 nm, between 50 nm and 200 nm, between 10 nm and 500 nm). In someembodiments, the RMS surface roughness may be less than or equal to 0.9μm, less than or equal to 0.8 μm, less than or equal to 0.7 μm, lessthan or equal to 0.6 μm, less than or equal to 0.5 μm, less than orequal to 0.4 μm, less than or equal to 0.3 μm, less than or equal to 0.2μm, less than or equal to 0.1 μm, less than or equal to 75 nm, less thanor equal to 50 nm, less than or equal to 25 nm, less than or equal to 10nm, less than or equal to 5 nm, less than or equal to 2 nm, less than orequal to 1 nm. In some embodiments, the RMS surface roughness may begreater than 1 nm, greater than 5 nm, greater than 10 nm, greater than50 nm, greater than 100 nm, greater than 200 nm, greater than 500 nm, orgreater than 700 nm. Other values are also possible. Combinations of theabove-noted ranges are also possible (e.g., a RMS surface roughness ofless than or equal to 0.5 μm and greater than 10 nm. A polymer layer ofa protective structure may have a RMS surface roughness of one or moreof the ranges noted above.

In embodiments in which a polymer layer is positioned on a substrate(e.g., an ion conductor layer), it should be appreciated that thepolymer layer may be cured or otherwise prepared directly onto thesubstrate, or the polymer may be added separately (e.g., as a commercialseparator) in other embodiments. A polymer structure either engineeredfor specific properties such as pore size, or one that is commerciallyavailable, such as battery separator material, may be used as a freestanding substrate for subsequent coatings as described herein. Incertain embodiments, the hole paths through the polymer layer may betortuous and may form a continuous path completely through the polymerlayer. Such hole paths may allow for electrolyte penetration up to theceramic coating, which may act as a fluid barrier and ion conductor foran electroactive species (e.g., lithium).

A polymer layer described herein can be made of a variety of materials.In some embodiments, the polymer layer can be a solid. In some cases,the polymer layer does not substantially include a solvent (like in agel), except for solvent that may pass through or reside in the pores ofthe polymer layer. In some embodiments, the polymer layer is porous. Thepolymer layer can be configured, according to some embodiments, toinhibit (e.g., prevent) physical contact between the first electrode andthe second electrode, which could result in short circuiting of theelectrochemical cell. The polymer layer can be configured to besubstantially electronically non-conductive, in certain embodiments,which can inhibit the degree to which the polymer layer causes shortcircuiting of the electrochemical cell. In certain embodiments, all orpart of the polymer layer can be formed of a material with a bulkelectronic resistivity of at least about 10⁴, at least about 10⁵, atleast about 10¹⁰, at least about 10¹⁵, or at least about 10²⁰Ohm-meters.

In some embodiments, the polymer can be ionically conductive, while inother embodiments, the polymer is substantially ionicallynon-conductive. In some embodiments, the average ionic conductivity ofthe polymer is at least about 10⁻⁷ S/cm, at least about 10⁻⁶ S/cm, atleast about 10⁻⁵ S/cm, at least about 10⁻⁴ S/cm, at least about 10⁻²S/cm, at least about 10⁻¹ S/cm. In certain embodiments, the averageionic conductivity of the polymer may be less than or equal to about 1S/cm, less than or equal to about 10⁻¹ S/cm, less than or equal to about10⁻² S/cm, less than or equal to about 10⁻³ S/cm, less than or equal toabout 10⁻⁴ S/cm, less than or equal to about 10⁻⁵ S/cm, less than orequal to about 10⁻⁶ S/cm, less than or equal to about 10⁻⁷ S/cm, or lessthan or equal to about 10⁻⁸ S/cm. Combinations of the above-referencedranges are also possible (e.g., an average ionic conductivity of atleast about 10⁻⁸ S/cm and less than or equal to about 10⁻¹ S/cm).Conductivity may be measured at room temperature (e.g., 25 degreesCelsius).

Examples of suitable polymer materials include, but are not limited to,polyolefins (e.g., polyethylenes and polypropylenes) and glass fiberfilter papers. Further examples of polymers and polymer materialssuitable for use include those comprising a microporous xerogel layer,for example, a microporous pseudo-boehmite layer, which may be providedeither as a free standing film or by a direct coating application on oneof the electrodes, as described in U.S. Pat. No. 6,153,337, filed Dec.19, 1997 and, entitled “Separators for electrochemical cells,” and U.S.Pat. No. 6,306,545 filed Dec. 17, 1998 and entitled “Separators forelectrochemical cells.” Solid electrolytes and gel electrolytes may alsofunction as a polymer layer in addition to their electrolyte function.Examples of useful gel polymer electrolytes include, but are not limitedto, those comprising one or more polymers selected from the groupconsisting of polyethylene oxides, polypropylene oxides,polyacrylonitriles, polysiloxanes, polyimides, polyphosphazenes,polyethers, sulfonated polyimides, perfluorinated membranes (NAFIONresins), polydivinyl polyethylene glycols, polyethylene glycoldiacrylates, polyethylene glycol dimethacrylates, derivatives of theforegoing, copolymers of the foregoing, crosslinked and networkstructures of the foregoing, and blends of the foregoing, andoptionally, one or more plasticizers.

Other classes polymers that may be suitable for use in the polymer layerinclude, but are not limited to, polyamines (e.g., poly(ethylene imine)and polypropylene imine (PPI)); polyamides (e.g., polyamide (Nylon),poly(ϵ-caprolactam) (Nylon 6), poly(hexamethylene adipamide) (Nylon66)), polyimides (e.g., polyimide, polynitrile, andpoly(pyromellitimide-1,4-diphenyl ether) (Kapton)); vinyl polymers(e.g., polyacrylamide, poly(2-vinyl pyridine), poly(N-vinylpyrrolidone),poly(methylcyanoacrylate), poly(ethylcyanoacrylate),poly(butylcyanoacrylate), poly(isobutylcyanoacrylate), poly(vinylacetate), poly (vinyl alcohol), poly(vinyl chloride), poly(vinylfluoride), poly(2-vinyl pyridine), vinyl polymer, polychlorotrifluoroethylene, and poly(isohexylcynaoacrylate)); polyacetals; polyolefins(e.g., poly(butene-1), poly(n-pentene-2), polypropylene,polytetrafluoroethylene); polyesters (e.g., polycarbonate, polybutyleneterephthalate, polyhydroxybutyrate); polyethers (poly(ethylene oxide)(PEO), poly(propylene oxide) (PPO), poly(tetramethylene oxide) (PTMO));vinylidene polymers (e.g., polyisobutylene, poly(methyl styrene),poly(methylmethacrylate) (PMMA), poly(vinylidene chloride), andpoly(vinylidene fluoride)); polyaramides (e.g., poly(imino-1,3-phenyleneiminoisophthaloyl) and poly(imino-1,4-phenylene iminoterephthaloyl));polyheteroaromatic compounds (e.g., polybenzimidazole (PBI),polybenzobisoxazole (PBO) and polybenzobisthiazole (PBT));polyheterocyclic compounds (e.g., polypyrrole); polyurethanes; phenolicpolymers (e.g., phenol-formaldehyde); polyalkynes (e.g., polyacetylene);polydienes (e.g., 1,2-polybutadiene, cis or trans-1,4-polybutadiene);polysiloxanes (e.g., poly(dimethylsiloxane) (PDMS),poly(diethylsiloxane) (PDES), polydiphenylsiloxane (PDPS), andpolymethylphenylsiloxane (PMPS)); and inorganic polymers (e.g.,polyphosphazene, polyphosphonate, polysilanes, polysilazanes). In someembodiments, the polymer may be selected from the group consisting ofpolyvinyl alcohol, polyisobutylene, epoxy, polyethylene, polypropylene,polytetrafluoroethylene, and combinations thereof. The mechanical andelectronic properties (e.g., conductivity, resistivity) of thesepolymers are known. Accordingly, those of ordinary skill in the art canchoose suitable polymers based on their mechanical and/or electronicproperties (e.g., ionic and/or electronic conductivity), and/or canmodify such polymers to be ionically conducting (e.g., conductivetowards single ions) based on knowledge in the art, in combination withthe description herein. For example, the polymer materials listed abovemay further comprise salts, for example, lithium salts (e.g., LiSCN,LiBr, LiI, LiClO₄, LiAsF₆, LiSO₃CF₃, LiSO₃CH₃, LiBF₄, LiB(Ph)₄, LiPF₆,LiC(SO₂CF₃)₃, and LiN(SO₂CF₃)₂), to enhance ionic conductivity.

Other suitable materials that could be used to form all or part of thepolymer layer include the polymer materials described in U.S. PatentPublication No. 2010/0327811, filed Jul. 1, 2010 and published Dec. 30,2010, entitled “Electrode Protection in Both Aqueous and Non-AqueousElectromechanical Cells, Including Rechargeable Lithium Batteries,”which is incorporated herein by reference in its entirety for allpurposes.

Those of ordinary skill in the art, given the present disclosure, wouldbe capable of selecting appropriate materials for use as a polymerlayer. Relevant factors that might be considered when making suchselections include the ionic conductivity of the polymer material; theability to deposit or otherwise form the polymer material on or withother materials in the electrochemical cell; the flexibility of thepolymer material; the porosity of the polymer material (e.g., overallporosity, pore size distribution, and/or tortuosity); the compatibilityof the polymer material with the fabrication process used to form theelectrochemical cell; the compatibility of the polymer material with theelectrolyte of the electrochemical cell; and/or the ability to adherethe polymer material to the ion conductor material. In certainembodiments, the polymer material can be selected based on its abilityto survive ion conductor deposition processes without mechanicallyfailing. For example, in embodiments in which relatively hightemperatures or high pressures are used to form the ion conductormaterial (e.g., a ceramic ion conductor material), the polymer materialcan be selected or configured to withstand such high temperatures andpressures.

Those of ordinary skill in the art can employ a simple screening test toselect an appropriate polymer material from candidate materials. Onesimple screening test involves positioning a material as a polymer layerin an electrochemical cell which, to function, requires passage of anionic species across the material (e.g., through pores of the material)while maintaining electronic separation. This is a simple test toemploy. If the material is substantially ionically conductive in thistest, then electrical current will be generated upon discharging theelectrochemical cell. Another simple screening test involves the abilityto increase the surface energy of the polymer by various methodsdescribed herein. A screening test may also involve testing the adhesionbetween the polymer and an ion conductor layer as described herein.Another screening test may involve testing the ability of the separatorto not swell in the presence of an electrolyte to be used in anelectrochemical cell. Other simple tests can be conducted by those ofordinary skill in the art.

The thickness of the polymer layer may vary. The thickness of thepolymer layer may be less than or equal to, e.g., 40 microns, less thanor equal to 30 microns, less than or equal to 25 microns, less than orequal to 10 microns, less than or equal to 5 microns, less than or equalto 3 microns, less than or equal to 2 microns, less than or equal to 1micron, less than or equal to 0.5 microns, less than or equal to 0.1microns, less than or equal to 0.05 microns. In some embodiments, thepolymer layer is at least 0.01 microns thick, at least 0.05 micronsthick, at least 0.1 microns thick, at least 0.5 microns thick, at least1 micron thick, at least 2 microns thick, at least 5 microns thick, atleast 10 microns thick, at least 20 microns thick, at least 25 micronsthick, at least 30 microns thick, or at least 40 microns thick. Otherthicknesses are also possible. Combinations of the above-noted rangesare also possible.

As described herein, a polymer layer may have a smooth surface. In someembodiments, the RMS surface roughness of a polymer layer may be, forexample, less than 1 μm. In certain embodiments, the RMS surfaceroughness for such surfaces may be, for example, between 0.5 nm and 1 μm(e.g., between 0.5 nm and 10 nm, between 10 nm and 50 nm, between 10 nmand 100 nm, between 50 nm and 200 nm, between 10 nm and 500 nm). In someembodiments, the RMS surface roughness may be less than or equal to 0.9μm, less than or equal to 0.8 μm, less than or equal to 0.7 μm, lessthan or equal to 0.6 μm, less than or equal to 0.5 μm, less than orequal to 0.4 μm, less than or equal to 0.3 μm, less than or equal to 0.2μm, less than or equal to 0.1 μm, less than or equal to 75 nm, less thanor equal to 50 nm, less than or equal to 25 nm, less than or equal to 10nm, less than or equal to 5 nm, less than or equal to 2 nm, less than orequal to 1 nm. In some embodiments, the RMS surface roughness may begreater than 1 nm, greater than 5 nm, greater than 10 nm, greater than50 nm, greater than 100 nm, greater than 200 nm, greater than 500 nm, orgreater than 700 nm. Other values are also possible. Combinations of theabove-noted ranges are also possible (e.g., a RMS surface roughness ofless than or equal to 0.5 μm and greater than 10 nm.

As described herein, the polymer layer may be porous. In someembodiments, the polymer pore size may be, for example, less than 5microns. In certain embodiments, the polymer pore size may be between 50nm and 5 microns, between 50 nm and 500 nm, between 100 nm and 300 nm,between 300 nm and 1 micron, between 500 nm and 5 microns. In someembodiments, the pore size may be less than or equal to 5 microns, lessthan or equal to 1 micron, less than or equal to 500 nm, less than orequal to 300 nm, less than or equal to 100 nm, or less than or equal to50 nm. In some embodiments, the pore size may be greater than 50 nm,greater than 100 nm, greater than 300 nm, greater than 500 nm, orgreater than 1 micron. Other values are also possible. Combinations ofthe above-noted ranges are also possible (e.g., a pore size of less than300 nm and greater than 100 nm).

As described herein, the relative thickness of the ion conductor layerto the average pore diameter of the polymer layer may influence thedegree of adhesive strength of the two layers. For instance, thethickness of the ion conductor layer may be greater than the averagepore diameter (or largest pore diameter) of polymer layer. In certainembodiments, the average thickness of the ion conductor layer is atleast 1.1 times, at least 1.2 times, at least 1.5 times, at least 1.7times, at least 2 times, at least 2.5 times, at least 2.7 times, atleast 2.8 times, at least 3.0 times, at least 3.2 times, at least 3.5times, at least 3.8 times, at least 4.0 times, at least 5.0 times, atleast 7.0 times, at least 10.0 times, or at least 20.0 times the averagepore size (or the largest pore diameter) of the polymer layer adjacentthe ion conductor layer. In certain embodiments, the average thicknessof the ion conductor layer may be less than or equal to 20.0 times, lessthan or equal to 10.0 times, less than or equal to 7.0 times, less thanor equal to 5.0 times, less than or equal to 4.0 times, less than orequal to 3.8 times, less than or equal to 3.5 times, less than or equalto 3.2 times, less than or equal to 3.0 times, less than or equal to 2.8times, less than or equal to 2.5 times, or less than or equal to 2 timesthe average pore size (or the largest pore diameter) of the polymerlayer adjacent the ion conductor layer. Other combinations of averagepore diameter and ion conductor layer thicknesses are also possible.

The ratio of thickness of the ion conductor layer to average porediameter of the polymer layer may be, for example, at least 1:1 (e.g.,1.1:1), at least 2:1, at least 3:2, at least 3:1, at least 4:1, at least5:1, or at least 10:1. The ratio of thickness of the ion conductor layerto average pore diameter of the polymer layer may be less than or equalto 10:1, less than or equal to 5:1, less than or equal to 3:1, less thanor equal to 2:1 (e.g., 1.1:1), or less than or equal to 1:1. Otherratios are also possible. Combinations of the above-noted ranges arealso possible.

The separator can be configured, according to some embodiments, toinhibit (e.g., prevent) physical contact between the first electrode andthe second electrode, which could result in short circuiting of theelectrochemical cell. The separator can be configured to besubstantially electronically non-conductive, which can inhibit thedegree to which the separator causes short circuiting of theelectrochemical cell. In certain embodiments, all or portions of theseparator can be formed of a material with a bulk electronic resistivityof at least about 10⁴, at least about 10⁵, at least about 10¹⁰, at leastabout 10¹⁵, or at least about 10²⁰ Ohm-meters. Bulk electronicresistivity may be measured at room temperature (e.g., 25 degreesCelsius).

In some embodiments, the separator can be ionically conductive, while inother embodiments, the separator is substantially ionicallynon-conductive. In some embodiments, the average ionic conductivity ofthe separator is at least about 10⁻⁷ S/cm, at least about 10⁻⁶ S/cm, atleast about 10⁻⁵ S/cm, at least about 10⁻⁴ S/cm, at least about 10⁻²S/cm, at least about 10⁻¹ S/cm. In certain embodiments, the averageionic conductivity of the separator may be less than or equal to about 1S/cm, less than or equal to about 10⁻¹ S/cm, less than or equal to about10⁻² S/cm, less than or equal to about 10⁻³ S/cm, less than or equal toabout 10⁻⁴ S/cm, less than or equal to about 10⁻⁵ S/cm, less than orequal to about 10⁻⁶ S/cm, less than or equal to about 10⁻⁷ S/cm, or lessthan or equal to about 10⁻⁸ S/cm. Combinations of the above-referencedranges are also possible (e.g., an average ionic conductivity of atleast about 10⁻⁸ S/cm and less than or equal to about 10⁻¹ S/cm).

In some embodiments, the separator can be a solid. The separator may beporous to allow an electrolyte solvent to pass through it. In somecases, the separator does not substantially include a solvent (like in agel), except for solvent that may pass through or reside in the pores ofthe separator. In other embodiments, a separator may be in the form of agel.

In certain embodiments, a separator may comprise a mixture of apolymeric binder, which may include one or more polymeric materialsdescribed herein (e.g., the polymers listed below for the separator),and a filler comprising a ceramic or a glassy/ceramic material, such asa material described herein for an ion conductor layer.

A separator as described herein can be made of a variety of materials.The separator may be polymeric in some instances, or formed of aninorganic material (e.g., glass fiber filter papers) in other instances.Examples of suitable separator materials include, but are not limitedto, polyolefins (e.g., polyethylenes, poly(butene-1), poly(n-pentene-2),polypropylene, polytetrafluoroethylene), polyamines (e.g., poly(ethyleneimine) and polypropylene imine (PPI)); polyamides (e.g., polyamide(Nylon), poly(ϵ-caprolactam) (Nylon 6), poly(hexamethylene adipamide)(Nylon 66)), polyimides (e.g., polyimide, polynitrile, andpoly(pyromellitimide-1,4-diphenyl ether) (Kapton®) (NOMEX®) (KEVLAR®));polyether ether ketone (PEEK); vinyl polymers (e.g., polyacrylamide,poly(2-vinyl pyridine), poly(N-vinylpyrrolidone),poly(methylcyanoacrylate), poly(ethylcyanoacrylate),poly(butylcyanoacrylate), poly(isobutylcyanoacrylate), poly(vinylacetate), poly (vinyl alcohol), poly(vinyl chloride), poly(vinylfluoride), poly(2-vinyl pyridine), vinyl polymer, polychlorotrifluoroethylene, and poly(isohexylcynaoacrylate)); polyacetals; polyesters(e.g., polycarbonate, polybutylene terephthalate, polyhydroxybutyrate);polyethers (poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO),poly(tetramethylene oxide) (PTMO)); vinylidene polymers (e.g.,polyisobutylene, poly(methyl styrene), poly(methylmethacrylate) (PMMA),poly(vinylidene chloride), and poly(vinylidene fluoride)); polyaramides(e.g., poly(imino-1,3-phenylene iminoisophthaloyl) andpoly(imino-1,4-phenylene iminoterephthaloyl)); polyheteroaromaticcompounds (e.g., polybenzimidazole (PBI), polybenzobisoxazole (PBO) andpolybenzobisthiazole (PBT)); polyheterocyclic compounds (e.g.,polypyrrole); polyurethanes; phenolic polymers (e.g.,phenol-formaldehyde); polyalkynes (e.g., polyacetylene); polydienes(e.g., 1,2-polybutadiene, cis or trans-1,4-polybutadiene); polysiloxanes(e.g., poly(dimethylsiloxane) (PDMS), poly(diethylsiloxane) (PDES),polydiphenylsiloxane (PDPS), and polymethylphenylsiloxane (PMPS)); andinorganic polymers (e.g., polyphosphazene, polyphosphonate, polysilanes,polysilazanes). In some embodiments, the polymer may be selected frompoly(n-pentene-2), polypropylene, polytetrafluoroethylene, polyamides(e.g., polyamide (Nylon), poly(ϵ-caprolactam) (Nylon 6),poly(hexamethylene adipamide) (Nylon 66)), polyimides (e.g.,polynitrile, and poly(pyromellitimide-1,4-diphenyl ether) (Kapton®)(NOMEX®) (KEVLAR®)), polyether ether ketone (PEEK), and combinationsthereof.

The mechanical and electronic properties (e.g., conductivity,resistivity) of these polymers are known. Accordingly, those of ordinaryskill in the art can choose suitable materials based on their mechanicaland/or electronic properties (e.g., ionic and/or electronicconductivity/resistivity), and/or can modify such polymers to beionically conducting (e.g., conductive towards single ions) based onknowledge in the art, in combination with the description herein. Forexample, the polymer materials listed above and herein may furthercomprise salts, for example, lithium salts (e.g., LiSCN, LiBr, LiI,LiClO₄, LiAsF₆, LiSO₃CF₃, LiSO₃CH₃, LiBF₄, LiB(Ph)₄, LiPF₆,LiC(SO₂CF₃)₃, and LiN(SO₂CF₃)₂), to enhance ionic conductivity, ifdesired.

Further examples of separators and separator materials suitable for useinclude those comprising a microporous xerogel layer, for example, amicroporous pseudo-boehmite layer, which may be provided either as afree standing film or by a direct coating application on one of theelectrodes, as described in U.S. Pat. No. 6,153,337, filed Dec. 19, 1997and, entitled “Separators for electrochemical cells,” and U.S. Pat. No.6,306,545 filed Dec. 17, 1998 and entitled “Separators forelectrochemical cells.” Solid electrolytes and gel electrolytes may alsofunction as a separator in addition to their electrolyte function.Examples of useful gel polymer electrolytes include, but are not limitedto, those comprising one or more polymers selected from the groupconsisting of polyethylene oxides, polypropylene oxides,polyacrylonitriles, polysiloxanes, polyimides, polyphosphazenes,polyethers, sulfonated polyimides, perfluorinated membranes (NAFIONresins), polydivinyl polyethylene glycols, polyethylene glycoldiacrylates, polyethylene glycol dimethacrylates, derivatives of theforegoing, copolymers of the foregoing, crosslinked and networkstructures of the foregoing, and blends of the foregoing, andoptionally, one or more plasticizers.

Other suitable materials that could be used to form all or part of theseparator include the separator materials described in U.S. PatentPublication No. 2010/0327811, filed Jul. 1, 2010 and published Dec. 30,2010, entitled “Electrode Protection in Both Aqueous and Non-AqueousElectromechanical Cells, Including Rechargeable Lithium Batteries,”which is incorporated herein by reference in its entirety for allpurposes.

Those of ordinary skill in the art, given the present disclosure, wouldbe capable of selecting appropriate materials for use as the separator.Relevant factors that might be considered when making such selectionsinclude the ionic conductivity of the separator material; the ability todeposit or otherwise form the separator material on or with othermaterials in the electrochemical cell; the flexibility of the separatormaterial; the porosity of the separator material (e.g., overallporosity, average pore size, pore size distribution, and/or tortuosity);the compatibility of the separator material with the fabrication processused to form the electrochemical cell; the compatibility of theseparator material with the electrolyte of the electrochemical cell;and/or the ability to adhere the separator material to the ion conductormaterial. In certain embodiments, the separator material can be selectedbased on its ability to survive ion conductor deposition processeswithout mechanically failing. For example, in embodiments in whichrelatively high temperatures or high pressures are used to form the ionconductor material (e.g., a ceramic ion conductor material), theseparator material can be selected or configured to withstand such hightemperatures and pressures.

Those of ordinary skill in the art can employ a simple screening test toselect an appropriate separator material from candidate materials. Onesimple screening test involves positioning a material as a separator inan electrochemical cell which, to function, requires passage of an ionicspecies across the material (e.g., through pores of the material) whilemaintaining electronic separation. If the material is substantiallyionically conductive in this test, then electrical current will begenerated upon discharging the electrochemical cell. Another simplescreening test involves the ability to increase the surface energy ofthe separator by various methods described herein. A screening test mayalso involve testing the adhesion between a polymer layer/separator andan ion conductor layer as described herein. Another screening test mayinvolve testing the ability of the polymer layer/separator to not swellin the presence of an electrolyte to be used in an electrochemical cell.Other simple tests can be conducted by those of ordinary skill in theart.

The thickness of the separator may vary. The thickness of the separatormay vary over a range from, for example, 5 microns to 40 microns. Forinstance, the thickness of the separator may be between 10-20 microns,between 20-30 microns, or between 20-40 microns. The thickness of theseparator may be less than or equal to, e.g., 40 microns, less than orequal to 30 microns, less than or equal to 25 microns, less than orequal to 10 microns, or less than or equal to 9 microns. In someembodiments, the separator is at least 9 microns thick, at least 10microns thick, at least 20 microns thick, at least 25 microns thick, atleast 30 microns thick, or at least 40 microns thick. Other thicknessesare also possible. Combinations of the above-noted ranges are alsopossible.

As described herein, a separator may have a smooth surface. In someembodiments, the RMS surface roughness of a separator may be, forexample, less than 1 μm. In certain embodiments, the RMS surfaceroughness for such surfaces may be, for example, between 0.5 nm and 1 μm(e.g., between 0.5 nm and 10 nm, between 10 nm and 50 nm, between 10 nmand 100 nm, between 50 nm and 200 nm, between 10 nm and 500 nm). In someembodiments, the RMS surface roughness may be less than or equal to 0.9μm, less than or equal to 0.8 μm, less than or equal to 0.7 μm, lessthan or equal to 0.6 μm, less than or equal to 0.5 μm, less than orequal to 0.4 μm, less than or equal to 0.3 μm, less than or equal to 0.2μm, less than or equal to 0.1 μm, less than or equal to 75 nm, less thanor equal to 50 nm, less than or equal to 25 nm, less than or equal to 10nm, less than or equal to 5 nm, less than or equal to 2 nm, less than orequal to 1 nm. In some embodiments, the RMS surface roughness may begreater than 1 nm, greater than 5 nm, greater than 10 nm, greater than50 nm, greater than 100 nm, greater than 200 nm, greater than 500 nm, orgreater than 700 nm. Other values are also possible. Combinations of theabove-noted ranges are also possible (e.g., a RMS surface roughness ofless than or equal to 0.5 μm and greater than 10 nm.

As described herein, the separator may be porous. In some embodiments,the separator pore size may be, for example, less than 5 microns. Incertain embodiments, the separator pore size may be between 50 nm and 5microns, between 50 nm and 500 nm, between 100 nm and 300 nm, between300 nm and 1 micron, between 500 nm and 5 microns. In some embodiments,the pore size may be less than or equal to 5 microns, less than or equalto 1 micron, less than or equal to 500 nm, less than or equal to 300 nm,less than or equal to 100 nm, or less than or equal to 50 nm. In someembodiments, the pore size may be greater than 50 nm, greater than 100nm, greater than 300 nm, greater than 500 nm, or greater than 1 micron.Other values are also possible. Combinations of the above-noted rangesare also possible (e.g., a pore size of less than 300 nm and greaterthan 100 nm).

As described herein, the relative thickness of the ion conductor layerto the average pore diameter of the separator, which is positionedadjacent the ion conductor layer, may influence the degree of adhesivestrength of the two layers. For instance, the thickness of the ionconductor layer may be greater than the average pore diameter (orlargest pore diameter) of separator. In certain embodiments, the averagethickness of the ion conductor layer is at least 1.1 times, at least 1.2times, at least 1.5 times, at least 1.7 times, at least 2 times, atleast 2.5 times, at least 2.7 times, at least 2.8 times, at least 3.0times, at least 3.2 times, at least 3.5 times, at least 3.8 times, atleast 4.0 times, at least 5.0 times, at least 7.0 times, at least 10.0times, or at least 20.0 times the average pore size (or the largest porediameter) of the separator adjacent the ion conductor layer. In certainembodiments, the average thickness of the ion conductor layer may beless than or equal to 20.0 times, less than or equal to 10.0 times, lessthan or equal to 7.0 times, less than or equal to 5.0 times, less thanor equal to 4.0 times, less than or equal to 3.8 times, less than orequal to 3.5 times, less than or equal to 3.2 times, less than or equalto 3.0 times, less than or equal to 2.8 times, less than or equal to 2.5times, or less than or equal to 2 times the average pore size (or thelargest pore diameter) of the separator adjacent the ion conductorlayer. Other combinations of average pore diameter and ion conductorlayer thicknesses are also possible.

The ratio of thickness of the ion conductor layer to average porediameter of the separator may be, for example, at least 1:1 (e.g.,1.1:1), at least 2:1, at least 3:2, at least 3:1, at least 4:1, at least5:1, or at least 10:1. The ratio of thickness of the ion conductor layerto average pore diameter of the separator may be less than or equal to10:1, less than or equal to 5:1, less than or equal to 3:1, less than orequal to 2:1 (e.g., 1.1:1), or less than or equal to 1:1. Other ratiosare also possible. Combinations of the above-noted ranges are alsopossible.

As described herein, various methods may be used to form an ionconductor/polymer (e.g., ion conductor/separator) composite. In certainembodiments in which a composite includes a polymer layer in the form ofa separator, the thickness of the composite ion conductor/polymer layersmay vary over a range from, for example, 5 microns to 40 microns. Forinstance, the thickness of the composite may be between 10-20 microns,between 20-30 microns, or between 20-40 microns. The thickness of thecomposite may be, for example, less than or equal to 40 microns, lessthan or equal to 30 microns, less than or equal to 25 microns, less thanor equal to 10 microns, less than or equal to 9 microns, or less than orequal to 7 microns. In some embodiments, the composite is at least 5microns thick, at least 7 microns thick, at least 9 microns thick, atleast 10 microns thick, at least 20 microns thick, at least 25 micronsthick, at least 30 microns thick, or at least 40 microns thick. Otherthicknesses are also possible. Combinations of the above-noted rangesare also possible.

As described herein, in some embodiments the pores of an ionconductor/polymer composite may be substantially unfilled with the ionconductor material. In some such embodiments, vacuum coating methodssuch as chemical vapor deposition, e-beam, sputtering, or thermalceramic deposition may be used to form the ion conductor layer. Othermethods, such as those described herein, can also be used.

In other instances, all or at least portions of the pores may be filledwith the ion conductor material. In some such embodiments, the ionconductor layer may be deposited by a vacuum sputtering process. Inother embodiments, a non-vacuum method such as infiltration by a slurryor gel, may also be suitable. Non-vacuum methods may especially be usedin instances in which there is a relatively high ratio of ion conductorthickness to pore diameter of the polymer. Other methods, such as thosedescribed herein, can also be used.

The relative aspect ratio of pore depth to pore diameter of the polymerlayer (e.g., separator) may influence whether or not the pores of thepolymer layer will be at least partially filled with the ion conductormaterial. In some embodiments, the aspect ratio of pore depth to porediameter of the polymer layer (e.g., separator) may range from, forexample, 0.1 to 10.0. In certain embodiments, the aspect ratio of poredepth to pore diameter may be at least 0.1, at least 0.2, at least 0.3,at least 0.5, at least 1.0, at least 2.0, at least 5.0, or at least10.0. The aspect ratio of pore depth to pore diameter may be, forexample, less than or equal to 10.0, less than or equal to 5.0, lessthan or equal to 2.0, less than or equal to 1.0, less than or equal to0.5, less than or equal to 0.3, less than or equal to 0.2, or less thanor equal to 0.1. Combinations of the above-referenced ranges are alsopossible. Other aspect ratios are also possible.

In certain embodiments, the aspect ratio of pore depth to pore diameteris greater than 0.3 in order to at least partially fill pores with anion conductive material using e-beam evaporation. Other methods such assputtering may also be suitable for pore filling with higher aspectratios.

In some embodiments, the average ionic conductivity (e.g., lithium ionconductivity) of the composite is at least about 10⁻⁷ S/cm, at leastabout 10⁻⁶ S/cm, at least about 10⁻⁵ S/cm, at least about 10⁴ S/cm, atleast about 10⁻² S/cm, at least about 10¹ S/cm, at least about 1 S/cm,at least about 10 S/cm. Conductivity may be measured at room temperature(e.g., 25 degrees Celsius).

A composite structure described herein including an ion conductor layerand a separator/polymer layer may be a free-standing structure that maybe packaged alone (optionally with suitable components such as asubstrate for handling), together with an electroactive material to forma protected electrode, or assembled into an electrochemical cell.

In certain embodiments, an electrochemical cell comprises a firstelectrode comprising an electroactive material, a second electrode and acomposite positioned between the first and second electrodes. Thecomposite comprises a separator comprising pores having an average poresize and an inorganic ion conductor layer bonded to the separator. Theseparator may have a bulk electronic resistivity of at least 10⁴ Ohmmeters, at least 10¹⁰ Ohm meters, or at least 10¹⁵ Ohm meters, e.g.,between 10¹⁰ Ohm meters to 10¹⁵ Ohm meters.

The inorganic ion conductor layer may have an ion (e.g., lithium ion)conductivity of at least 10⁻⁶ S/cm at 25 degrees Celsius. In certainembodiments, the inorganic ion conductor layer has an ion (e.g., lithiumion) conductivity of at least 10⁻⁵ S/cm, at least 10⁻⁴ S/cm, or at least10⁻³ S/cm at 25 degrees Celsius.

The inorganic ion conductor layer may comprises a ceramic, a glass, or aglass-ceramic. In one set of embodiments, the inorganic ion conductorlayer comprises an lithium oxysulfide.

The strength of adhesion between the separator and the inorganic ionconductor layer may be sufficiently strong to pass the tape testaccording to the standard ASTM D3359-02, in some instances. The strengthof adhesion between the separator and the inorganic ion conductor layermay be, in some cases, at least 350 N/m or at least 500 N/m. In someembodiments, the inorganic ion conductor layer is bonded to theseparator by covalent bonding. Covalent bonding may be achieved bysuitable methods described herein, and one embodiment, involves plasmatreatment of the separator prior to addition or joining of the inorganicion conductor layer and the separator.

In some embodiments, a ratio of a thickness of the inorganic ionconductor layer to the average pore size of the separator is at least1.1:1 (e.g., at least 2:1, at least 3:1, or at least 5:1).

In some embodiments, the inorganic ion conductor layer has a thicknessof less than or equal to 2.0 microns, less than or equal to 1.5 microns,less than or equal to 1.3 microns, less than or equal to 1 micron, lessthan or equal to 800 nm, less than or equal to 600 nm, or between 400 nmand 600 nm.

In some embodiments, a separator having a thickness between 5 micronsand 40 microns is included. In certain embodiments, the separator is asolid, polymeric separator. For instance, the separator may comprises orbe formed of one or more of poly(n-pentene-2), polypropylene,polytetrafluoroethylene, a polyamide (e.g., polyamide (Nylon),poly(ϵ-caprolactam) (Nylon 6), poly(hexamethylene adipamide) (Nylon66)), a polyimide (e.g., polynitrile, andpoly(pyromellitimide-1,4-diphenyl ether) (Kapton®) (NOMEX®) (KEVLAR®)),polyether ether ketone (PEEK), and combinations thereof. The separatormay also comprise or be formed of other polymers or materials describedherein.

In certain embodiments, a separator may comprise a mixture of apolymeric binder and a filler comprising a ceramic or a glassy/ceramicmaterial, such as a material described herein for an ion conductorlayer.

The separator may have an average pore size of less than or equal to 5microns, less than or equal to 1 micron, less than or equal to 0.5microns, between 0.05-5 microns, or between 0.1-0.3 microns.

The composite may have an air permeation time of at least 20,000Gurley-s, at least 40,000 Gurley-s, at least 60,000 Gurley-s, at least80,000 Gurley-s, at least 100,000 Gurley-s, or at least 120,000 Gurley-saccording to Gurley test TAPPI Standard T 536 om-12. The composite mayhave an air permeation time of less than or equal to 300,000 Gurley-saccording to Gurley test TAPPI Standard T 536 om-12.

The composite may be formed by, for example, depositing the inorganicion conductor layer onto the separator by a vacuum deposition processsuch as electron beam evaporation or by a sputtering process.

Although the composites described herein may be used in variouselectrochemical cells, in one set of embodiments, the composite isincluded in a lithium cell, such as a lithium-sulfur cell. Accordingly,a first electrode may comprise lithium, such as lithium metal and/or alithium alloy, as a first electroactive material, and a second electrodecomprises sulfur as a second electroactive material.

In one set of embodiments, the electrochemical cell is a lithium-sulfurcell comprising a first electrode comprising lithium, a second electrodecomprising sulfur, a separator arranged between said first electrode andsaid second electrode, and a solid ion conductor contacting and/orbonded to the separator.

In some embodiments, the solid ion conductor is an inorganic ionconductor layer bonded to the separator, wherein a ratio of a thicknessof the inorganic ion conductor layer to the average pore size of theseparator is at least 1.1:1.

In embodiments in which a polymer layer is positioned on a substrate(e.g., an ion conductor layer), e.g., as part of a multi-layerprotective structure, it should be appreciated that the polymer layermay be cured or otherwise prepared directly onto the substrate, or thepolymer may be added separately to the substrate.

The polymer layer can be a solid (e.g., as opposed to a gel). Thepolymer layer can be configured to be electronically non-conductive, incertain embodiments, and may be formed of a material with a bulkelectronic resistivity of at least about 10⁴, at least about 10⁵, atleast about 10¹⁰, at least about 10¹⁵, or at least about 10²⁰Ohm-meters.

In some embodiments, the polymer can be ionically conductive. In someembodiments, the average ionic conductivity of the polymer is at leastabout 10⁻⁷ S/cm, at least about 10⁻⁶ S/cm, at least about 10⁻⁵ S/cm, atleast about 10⁻⁴ S/cm, at least about 10⁻² S/cm, at least about 10⁻¹S/cm. In certain embodiments, the average ionic conductivity of thepolymer may be less than or equal to about 1 S/cm, less than or equal toabout 10⁻¹ S/cm, less than or equal to about 10⁻² S/cm, less than orequal to about 10⁻³ S/cm, less than or equal to about 10⁻⁴ S/cm, lessthan or equal to about 10⁻⁵ S/cm, less than or equal to about 10⁻⁶ S/cm,less than or equal to about 10⁻⁷ S/cm, or less than or equal to about10⁻⁸ S/cm. Combinations of the above-referenced ranges are also possible(e.g., an average ionic conductivity of at least about 10⁻⁸ S/cm andless than or equal to about 10⁻¹ S/cm). Conductivity may be measured atroom temperature (e.g., 25 degrees Celsius).

A polymer layer described herein can be made of a variety of materials.Examples of materials that may be suitable for use in the polymer layerinclude, but are not limited to, polyamines (e.g., poly(ethylene imine)and polypropylene imine (PPI)); polyamides (e.g., polyamide (Nylon),poly(ϵ-caprolactam) (Nylon 6), poly(hexamethylene adipamide) (Nylon66)), polyimides (e.g., polyimide, polynitrile, andpoly(pyromellitimide-1,4-diphenyl ether) (Kapton)); vinyl polymers(e.g., polyacrylamide, poly(2-vinyl pyridine), poly(N-vinylpyrrolidone),poly(methylcyanoacrylate), poly(ethylcyanoacrylate),poly(butylcyanoacrylate), poly(isobutylcyanoacrylate), poly(vinylacetate), poly (vinyl alcohol), poly(vinyl chloride), poly(vinylfluoride), poly(2-vinyl pyridine), vinyl polymer, polychlorotrifluoroethylene, and poly(isohexylcynaoacrylate)); polyacetals; polyolefins(e.g., poly(butene-1), poly(n-pentene-2), polypropylene,polytetrafluoroethylene); polyesters (e.g., polycarbonate, polybutyleneterephthalate, polyhydroxybutyrate); polyethers (poly(ethylene oxide)(PEO), poly(propylene oxide) (PPO), poly(tetramethylene oxide) (PTMO));vinylidene polymers (e.g., polyisobutylene, poly(methyl styrene),poly(methylmethacrylate) (PMMA), poly(vinylidene chloride), andpoly(vinylidene fluoride)); polyaramides (e.g., poly(imino-1,3-phenyleneiminoisophthaloyl) and poly(imino-1,4-phenylene iminoterephthaloyl));polyheteroaromatic compounds (e.g., polybenzimidazole (PBI),polybenzobisoxazole (PBO) and polybenzobisthiazole (PBT));polyheterocyclic compounds (e.g., polypyrrole); polyurethanes; phenolicpolymers (e.g., phenol-formaldehyde); polyalkynes (e.g., polyacetylene);polydienes (e.g., 1,2-polybutadiene, cis or trans-1,4-polybutadiene);polysiloxanes (e.g., poly(dimethylsiloxane) (PDMS),poly(diethylsiloxane) (PDES), polydiphenylsiloxane (PDPS), andpolymethylphenylsiloxane (PMPS)); and inorganic polymers (e.g.,polyphosphazene, polyphosphonate, polysilanes, polysilazanes). In someembodiments, the polymer may be selected from the group consisting ofpolyvinyl alcohol, polyisobutylene, epoxy, polyethylene, polypropylene,polytetrafluoroethylene, and combinations thereof. The mechanical andelectronic properties (e.g., conductivity, resistivity) of thesepolymers are known. Accordingly, those of ordinary skill in the art canchoose suitable polymers based on their mechanical and/or electronicproperties (e.g., ionic and/or electronic conductivity), and/or canmodify such polymers to be ionically conducting (e.g., conductivetowards single ions) based on knowledge in the art, in combination withthe description herein. For example, the polymer materials listed abovemay further comprise salts, for example, lithium salts (e.g., LiSCN,LiBr, LiI, LiClO₄, LiAsF₆, LiSO₃CF₃, LiSO₃CH₃, LiBF₄, LiB(Ph)₄, LiPF₆,LiC(SO₂CF₃)₃, and LiN(SO₂CF₃)₂), to enhance ionic conductivity.

Those of ordinary skill in the art, given the present disclosure, wouldbe capable of selecting appropriate materials for use as a polymerlayer. Relevant factors that might be considered when making suchselections include the ionic conductivity of the polymer material; theability to deposit or otherwise form the polymer material on or withother materials in the electrochemical cell; the flexibility of thepolymer material; the porosity of the polymer material (e.g., overallporosity, pore size distribution, and/or tortuosity); the compatibilityof the polymer material with the fabrication process used to form theelectrochemical cell; the compatibility of the polymer material with theelectrolyte of the electrochemical cell; and/or the ability to adherethe polymer material to the ion conductor material.

The thickness of the polymer layer may vary. The thickness of thepolymer layer may be less than or equal to, e.g., 40 microns, less thanor equal to 30 microns, less than or equal to 25 microns, less than orequal to 10 microns, less than or equal to 5 microns, less than or equalto 3 microns, less than or equal to 2 microns, less than or equal to 1micron, less than or equal to 0.5 microns, less than or equal to 0.1microns, less than or equal to 0.05 microns. In some embodiments, thepolymer layer is at least 0.01 microns thick, at least 0.05 micronsthick, at least 0.1 microns thick, at least 0.5 microns thick, at least1 micron thick, at least 2 microns thick, at least 5 microns thick, atleast 10 microns thick, at least 20 microns thick, at least 25 micronsthick, at least 30 microns thick, or at least 40 microns thick. Otherthicknesses are also possible. Combinations of the above-noted rangesare also possible.

In some embodiments, an electrode, such as a first electrode (e.g.,electrode 102 in FIGS. 1A and 1B) comprises an electroactive materialcomprising lithium. Suitable electroactive materials comprising lithiuminclude, but are not limited to, lithium metal (such as lithium foiland/or lithium deposited onto a conductive substrate) and lithium metalalloys (e.g., lithium-aluminum alloys and lithium-tin alloys). In someembodiments, the electroactive lithium-containing material of anelectrode comprises greater than 50 wt % lithium. In some cases, theelectroactive lithium-containing material of an electrode comprisesgreater than 75 wt % lithium. In still other embodiments, theelectroactive lithium-containing material of an electrode comprisesgreater than 90 wt % lithium. Other examples of electroactive materialsthat can be used (e.g., in the first electrode, which can be a negativeelectrode) include, but are not limited to, other alkali metals (e.g.,sodium, potassium, rubidium, caesium, francium), alkaline earth metals(e.g., beryllium, magnesium, calcium, strontium, barium, radium), andthe like. In some embodiments, the first electrode is an electrode for alithium ion electrochemical cell. In some cases, the first electrode isan anode or negative electrode.

The second electrode (e.g., electrode 102 in FIGS. 1A and 1B) cancomprise a variety of suitable electroactive materials. In some cases,the second electrode is a cathode or positive electrode.

In some embodiments, the electroactive material within an electrode(e.g., within a positive electrode) can comprise metal oxides, such asLiCoO₂, LiCo_(x)Ni_((1-x))O₂, LiCo_(x)Ni_(y)Mn_((l-x-y)) (e.g.,LiNi_(1/3)Mn_(1/3)CO_(1/3)O₂), LiMn₂O₄, and combinations thereof. Insome embodiments, the electrode active material within an electrode(e.g., within a positive electrode) can comprise lithium transitionmetal phosphates (e.g., LiFePO₄), which can, in certain embodiments, besubstituted with borates and/or silicates.

In certain embodiments, the electroactive material within an electrode(e.g., within a positive electrode) can comprise electroactivetransition metal chalcogenides, electroactive conductive polymers,and/or electroactive sulfur-containing materials, and combinationsthereof. As used herein, the term “chalcogenides” pertains to compoundsthat contain one or more of the elements of oxygen, sulfur, andselenium. Examples of suitable transition metal chalcogenides include,but are not limited to, the electroactive oxides, sulfides, andselenides of transition metals selected from the group consisting of Mn,V, Cr, Ti, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Hf. Ta, W, Re,Os, and Ir. In one embodiment, the transition metal chalcogenide isselected from the group consisting of the electroactive oxides ofnickel, manganese, cobalt, and vanadium, and the electroactive sulfidesof iron. In one embodiment, an electrode (e.g., a positive electrode)can comprise an electroactive conductive polymer. Examples of suitableelectroactive conductive polymers include, but are not limited to,electroactive and electronically conductive polymers selected from thegroup consisting of polypyrroles, polyanilines, polyphenylenes,polythiophenes, and polyacetylenes. In certain embodiments, it may bedesirable to use polypyrroles, polyanilines, and/or polyacetylenes asconductive polymers.

In certain embodiments, the electrode active material within anelectrode (e.g., within a positive electrode) can comprise sulfur. Insome embodiments, the electroactive material within an electrode cancomprise electroactive sulfur-containing materials. “Electroactivesulfur-containing materials,” as used herein, refers to electrode activematerials which comprise the element sulfur in any form, wherein theelectrochemical activity involves the oxidation or reduction of sulfuratoms or moieties. As an example, the electroactive sulfur-containingmaterial may comprise elemental sulfur (e.g., S₈). In some embodiments,the electroactive sulfur-containing material comprises a mixture ofelemental sulfur and a sulfur-containing polymer. Thus, suitableelectroactive sulfur-containing materials may include, but are notlimited to, elemental sulfur, sulfides or polysulfides (e.g., of alkalimetals) which may be organic or inorganic, and organic materialscomprising sulfur atoms and carbon atoms, which may or may not bepolymeric. Suitable organic materials include, but are not limited to,those further comprising heteroatoms, conductive polymer segments,composites, and conductive polymers. In some embodiments, anelectroactive sulfur-containing material within an electrode (e.g., apositive electrode) comprises at least about 40 wt % sulfur. In somecases, the electroactive sulfur-containing material comprises at leastabout 50 wt %, at least about 75 wt %, or at least about 90 wt % sulfur.

Examples of sulfur-containing polymers include those described in: U.S.Pat. Nos. 5,601,947 and 5,690,702 to Skotheim et al.; U.S. Pat. Nos.5,529,860 and 6,117,590 to Skotheim et al.; U.S. Pat. No. 6,201,100issued Mar. 13, 2001, to Gorkovenko et al., and PCT Publication No. WO99/33130. Other suitable electroactive sulfur-containing materialscomprising polysulfide linkages are described in U.S. Pat. No. 5,441,831to Skotheim et al.; U.S. Pat. No. 4,664,991 to Perichaud et al., and inU.S. Pat. Nos. 5,723,230, 5,783,330, 5,792,575 and 5,882,819 to Naoi etal. Still further examples of electroactive sulfur-containing materialsinclude those comprising disulfide groups as described, for example in,U.S. Pat. No. 4,739,018 to Armand et al.; U.S. Pat. Nos. 4,833,048 and4,917,974, both to De Jonghe et al.; U.S. Pat. Nos. 5,162,175 and5,516,598, both to Visco et al.; and U.S. Pat. No. 5,324,599 to Oyama etal.

While sulfur is described predominately as an electroactive species inthe second electrode (which can be, for example, a porous positiveelectrode), it is to be understood that wherever sulfur is described asa component of an electroactive material within an electrode herein, anysuitable electroactive species may be used. For example, in certainembodiments, the electroactive species within the second electrode(e.g., a porous positive electrode) can comprise a hydrogen-absorbingalloy, such as those commonly used in nickel metal hydride batteries.One of ordinary skill in the art, given the present disclosure, would becapable of extending the ideas described herein to electrochemical cellscontaining electrodes employing other active materials.

The embodiments described herein may be used in association with anytype of electrochemical cell. In certain embodiments, theelectrochemical cell is a primary (non-rechargeable) battery. In otherembodiments, the electrochemical cell may be a secondary (rechargeable)battery. Certain embodiments relate to lithium rechargeable batteries.In certain embodiments, the electrochemical cell comprises alithium-sulfur rechargeable battery. However, wherever lithium batteriesare described herein, it is to be understood that any analogous alkalimetal battery can be used. Additionally, although embodiments of theinvention are particularly useful for protection of a lithium anode, theembodiments described herein may be applicable to other applications inwhich electrode protection is desired.

Any suitable electrolyte may be used in the electrochemical cellsdescribed herein. Generally, the choice of electrolyte will depend uponthe chemistry of the electrochemical cell, and, in particular, thespecies of ion that is to be transported between electrodes in theelectrochemical cell. Suitable electrolytes can comprise, in someembodiments, one or more ionic electrolyte salts to provide ionicconductivity and one or more liquid electrolyte solvents, gel polymermaterials, or other polymer materials. Examples of useful non-aqueousliquid electrolyte solvents include, but are not limited to, non-aqueousorganic solvents, such as, for example, N-methyl acetamide,acetonitrile, acetals, ketals, esters, carbonates, sulfones, sulfites,sulfolanes, aliphatic ethers, cyclic ethers, glymes, polyethers,phosphate esters, siloxanes, dioxolanes (e.g., 1,3-dioxolane),N-alkylpyrrolidones, bis(trifluoromethanesulfonyl)imide, substitutedforms of the foregoing, and blends thereof. Fluorinated derivatives ofthe foregoing are also useful as liquid electrolyte solvents. In somecases, aqueous solvents can be used as electrolytes for lithium cells.Aqueous solvents can include water, which can contain other componentssuch as ionic salts. In some embodiments, the electrolyte can includespecies such as lithium hydroxide, or other species rendering theelectrolyte basic, so as to reduce the concentration of hydrogen ions inthe electrolyte.

The electrolyte can comprise one or more ionic electrolyte salts toprovide ionic conductivity. In some embodiments, one or more lithiumsalts (e.g., LiSCN, LiBr, LiI, LiClO₄, LiAsF₆, LiSO₃CF₃, LiSO₃CH₃,LiBF₄, LiB(Ph)₄, LiPF₆, LiC(SO₂CF₃)₃ and LiN(SO₂CF₃)₂) can be included.Other electrolyte salts that may be useful include lithium polysulfides(Li₂S_(x)), and lithium salts of organic ionic polysulfides(LiS_(x)R)_(n), where x is an integer from 1 to 20, n is an integer from1 to 3, and R is an organic group, and those disclosed in U.S. Pat. No.5,538,812 to Lee et al. A range of concentrations of the ionic lithiumsalts in the solvent may be used such as from about 0.2 m to about 2.0 m(m is moles/kg of solvent). In some embodiments, a concentration in therange between about 0.5 m to about 1.5 m is used. The addition of ioniclithium salts to the solvent is optional in that upon discharge of Li/Scells the lithium sulfides or polysulfides formed typically provideionic conductivity to the electrolyte, which may make the addition ofionic lithium salts unnecessary.

It should be understood that the electrochemical cells and componentsshown in is the figures are exemplary, and the orientation of thecomponents can be varied. Additionally, non-planar arrangements,arrangements with proportions of materials different than those shown,and other alternative arrangements are useful in connection with certainembodiments of the present invention. A typical electrochemical cellcould also include, for example, a containment structure, currentcollectors, external circuitry, and the like. Those of ordinary skill inthe art are well aware of the many arrangements that can be utilizedwith the general schematic arrangement as shown in the figures anddescribed herein.

The following documents are incorporated herein by reference in theirentireties for all purposes: U.S. Pat. No. 7,247,408, filed May 23,2001, entitled “Lithium Anodes for Electrochemical Cells”; U.S. Pat. No.5,648,187, filed Mar. 19, 1996, entitled “Stabilized Anode forLithium-Polymer Batteries”; U.S. Pat. No. 5,961,672, filed Jul. 7, 1997,entitled “Stabilized Anode for Lithium-Polymer Batteries”; U.S. Pat. No.5,919,587, filed May 21, 1997, entitled “Novel Composite Cathodes,Electrochemical Cells Comprising Novel Composite Cathodes, and Processesfor Fabricating Same”; U.S. patent application Ser. No. 11/400,781,filed Apr. 6, 2006, published as U.S. Pub. No. 2007-0221265, andentitled “Rechargeable Lithium/Water, Lithium/Air Batteries”;International Patent Apl. Serial No.: PCT/US2008/009158, filed Jul. 29,2008, published as International Pub. No. WO/2009017726, and entitled“Swelling Inhibition in Lithium Batteries”; U.S. patent application Ser.No. 12/312,764, filed May 26, 2009, published as U.S. Pub. No.2010-0129699, and entitled “Separation of Electrolytes”; InternationalPatent Apl. Serial No.: PCT/US2008/012042, filed Oct. 23, 2008,published as International Pub. No. WO/2009054987, and entitled “Primerfor Battery Electrode”; U.S. patent application Ser. No. 12/069,335,filed Feb. 8, 2008, published as U.S. Pub. No. 2009-0200986, andentitled “Protective Circuit for Energy-Storage Device”; U.S. patentapplication Ser. No. 11/400,025, filed Apr. 6, 2006, published as U.S.Pub. No. 2007-0224502, and entitled “Electrode Protection in bothAqueous and Non-Aqueous Electrochemical Cells, including RechargeableLithium Batteries”; U.S. patent application Ser. No. 11/821,576, filedJun. 22, 2007, published as U.S. Pub. No. 2008/0318128, and entitled“Lithium Alloy/Sulfur Batteries”; patent application Ser. No.11/111,262, filed Apr. 20, 2005, published as U.S. Pub. No.2006-0238203, and entitled “Lithium Sulfur Rechargeable Battery FuelGauge Systems and Methods”; U.S. patent application Ser. No. 11/728,197,filed Mar. 23, 2007, published as U.S. Pub. No. 2008-0187663, andentitled “Co-Flash Evaporation of Polymerizable Monomers andNon-Polymerizable Carrier Solvent/Salt Mixtures/Solutions”;International Patent Apl. Serial No.: PCT/US2008/010894, filed Sep. 19,2008, published as International Pub. No. WO/2009042071, and entitled“Electrolyte Additives for Lithium Batteries and Related Methods”;International Patent Apl. Serial No.: PCT/US2009/000090, filed Jan. 8,2009, published as International Pub. No. WO/2009/089018, and entitled“Porous Electrodes and Associated Methods”; U.S. patent application Ser.No. 12/535,328, filed Aug. 4, 2009, published as U.S. Pub. No.2010/0035128, and entitled “Application of Force In ElectrochemicalCells”; U.S. patent application Ser. No. 12/727,862, filed Mar. 19,2010, entitled “Cathode for Lithium Battery”; U.S. patent applicationSer. No. 12,471,095, filed May 22, 2009, entitled “Hermetic SampleHolder and Method for Performing Microanalysis Under ControlledAtmosphere Environment”; U.S. patent application Ser. No. 12/862,513,filed on Aug. 24, 2010, entitled “Release System for Electrochemicalcells (which claims priority to Provisional Patent Apl. Ser. No.61/236,322, filed Aug. 24, 2009, entitled “Release System forElectrochemical Cells”); U.S. patent application Ser. No. 13/216,559,filed on Aug. 24, 2011, published as U.S. Patent Publication No.2012/0048729, entitled “Electrically Non-Conductive Materials forElectrochemical Cells;” U.S. Provisional Patent Apl. Ser. No.61/376,554, filed on Aug. 24, 2010, entitled “ElectricallyNon-Conductive Materials for Electrochemical Cells;” U.S. patentapplication Ser. No. 12/862,528, filed on Aug. 24, 2010, published asU.S. Patent Publication No. 2011/0177398, entitled “ElectrochemicalCell;” U.S. patent application Ser. No. 12/862,563, filed on Aug. 24,2010, published as U.S. Pub. No. 2011/0070494, entitled “ElectrochemicalCells Comprising Porous Structures Comprising Sulfur”; U.S. patentapplication Ser. No. 12/862,551, filed on Aug. 24, 2010, published asU.S. Pub. No. 2011/0070491, entitled “Electrochemical Cells ComprisingPorous Structures Comprising Sulfur”; U.S. patent application Ser. No.12/862,576, filed on Aug. 24, 2010, published as U.S. Pub. No.2011/0059361, entitled “Electrochemical Cells Comprising PorousStructures Comprising Sulfur”; U.S. patent application Ser. No.12/862,581, filed on Aug. 24, 2010, published as U.S. Pub. No.2011/0076560, entitled “Electrochemical Cells Comprising PorousStructures Comprising Sulfur”; U.S. patent application Ser. No.13/240,113, filed on Sep. 22, 2011, published as U.S. Patent Pub. No.2012/0070746, entitled “Low Electrolyte Electrochemical Cells”; U.S.Patent Apl. Ser. No. 61/385,343, filed on Sep. 22, 2010, entitled “LowElectrolyte Electrochemical Cells”; and U.S. patent application Ser. No.13/033,419, filed Feb. 23, 2011, published as U.S. Patent Pub. No.2011/0206992, entitled “Porous Structures for Energy Storage Devices”;U.S. patent application Ser. No. 13/789,783, filed Mar. 9, 2012,published as U.S. Patent Pub. No. 2013/0252103, and entitled “PorousSupport Structures, Electrodes Containing Same, and Associated Methods”;U.S. patent Ser. No. 13/644,933, filed Oct. 4, 2012, published as U.S.Patent Pub. No. 2013/0095380, and entitled “Electrode Structure andMethod for Making the Same”; U.S. patent application Ser. No.14/150,156, filed Jan. 8, 2014, and entitled “Conductivity Control inElectrochemical Cells”; U.S. patent application Ser. No. 13/833,377,filed Mar. 15, 2013, and entitled “Protective Structures forElectrodes”; and U.S. Provisional Patent Apl. No. 61/787,897, filed Mar.15, 2013, and entitled “Protected Electrode Structures and Methods”. Allother patents and patent applications disclosed herein are alsoincorporated by reference in their entirety for all purposes.

The following example is intended to illustrate certain embodiments ofthe present invention, but does not exemplify the full scope of theinvention.

EXAMPLES Example 1A

This example describes a method for generating an ion conductor layer ona free-standing separator (e.g., an ion conductor-separator composite),with improved adhesive strength between the layers.

A commercial separator, Celgard 2400, having a pore diameter between 100nm to 200 nm, was used as a substrate. The separator was pre-treatedwith plasma using an Anode Layer Ion Source in a chamber at a pressureof 10⁻³ Torr, a power of 50 W, in the presence of argon gas. Thetreatment continued for 7 minutes. Before plasma treatment, the surfaceenergy of the separator was 32 dynes. The separator surface energy afterplasma treatment was greater than 70 dynes, as measured by a dyne penset.

Next, a layer of lithium oxysulfide, an ion conductor, was depositedonto the separator to form an ion conductor layer by e-beam evaporation.The major components of the lithium oxysulfide layer were lithium,silicon, sulfur and oxygen, with the following ratios: 1.5:1 for Si:O,4.5:1 for S:O, and 3.1:1 for S:Si. In three experiments, the thicknessof the ion conductor layer ranged from about 600-800 nm, as shown inFIGS. 11A-11C. The ratio of thickness of the ion conductor layer to porediameter of the separator in these experiments ranged from about 3:1 to8:1.

FIGS. 11A, 11B, and 11C are scanning electron microscopy (SEM) imagesshowing the ion conductor (lithium oxysulfide) coating on the commercialseparator. FIG. 11A is an SEM of the lithium oxysulfide coating on a25-micron-thick separator. The thickness of the lithium oxysulfide layerwas 610 nm. FIG. 11B is an SEM of a lithium oxysulfide layer on a 25micron separator. The thickness of the lithium oxysulfide layer was 661nm. FIG. 11C is an SEM cross-sectional image of an 800 nm thick lithiumoxysulfide coating on the separator material. These images also showthat the lithium oxysulfide material did not penetrate into theseparator's pores.

A tape test was performed according to standard ASTM-D3359-02 todetermine adhesiveness between the ion conductor layer and theseparator. The test demonstrated that the ion conductor was well bondedto the separator and did not delaminate from the separator.

This example shows that pre-treatment of the surface of the separatorwith plasma prior to deposition of an ion conductor (lithium oxysulfide)layer enhanced adhesion of the ion conductor layer to the separator,compared to the absence of a pre-treatment step (Comparative Example 1).

Example 1B

An ion conductor-separator composite similar to that described inExample 1A was formed except the lithium oxysulfide ion conductor layerhad a thickness of 1 micron. The surface of the separator was treated toplasma as described in Example 1A prior to deposition of the lithiumoxysulfide layer.

The final composite demonstrated 17 times reduced air permeation ratescompared with an untreated separator (i.e., a separator that was nottreated to plasma prior to deposition of the lithium oxysulfide layer,Comparative Example 1), as determined by a Gurley test performed with apressure differential of 3 kPa (TAPPI Standard T 536 om-12). The finalcomposite had an air permeation time of over 168 minutes, compared toabout 9.7 minutes for the composite including the untreated separator(Comparative Example 1).

This example shows that pre-treatment of the surface of the separatorwith plasma prior to deposition of an ion conductor (lithium oxysulfide)layer enhanced air permeation time of the composite, compared to acomposite that included an untreated separator (Comparative Example 1).

Comparative Example 1

The following is a comparative example describing an ion conductor layerthat was poorly bonded to a separator.

The method described in Example 1 was used to form an ionconductor-separator composite, except here the separator was not treatedwith plasma prior to deposition of the ion conductor layer.

The ion conductor-separator composite did not pass the tape test,demonstrating delamination of the ion conductor layer from theseparator.

At a ceramic thickness of 1 micron, the air permeation time was below9.7 minutes as determined by a Gurley Test (TAPPI Standard T 536 om-12).

Example 2

This example shows the formation and performance of the ionconductor-separator composite of Example 1 in a lithium-sulfurelectrochemical cell.

The ion conductor (lithium oxysulfide)-coated separator of Example 1 wasvacuum coated with metallic lithium (˜25 microns of lithium deposited ontop of the lithium oxysulfide layer). The lithium anode was protectedwith the lithium oxysulfide-coated separator and was assembled into alithium-sulfur battery cell.

The cathode contained 55% weight percent sulfur, 40% weight percent ofcarbon black and 5% weight percent of polyvinyl alcohol binder. Thesulfur surface loading was approximately 2 mg/cm².

The active electrode covered a total surface area of 16.57 cm². Thelithium-sulfur battery cells were filled with an electrolyte containing16% weight percent of lithium bis(Trifluoromethanesulfonyl)imide, 42%weight percent of dimethoxyethane, and 42% weight percent of1,3-dioxolane solvents.

The lithium-sulfur battery cells were discharged at 3 mA to 1.7 V andwere charged at 3 mA. Charge was terminated when the lithium-sulfurbattery cell reached 2.5 V or when charge time exceeded 15 hours if thecells were not able reaching 2.5 V.

The lithium-sulfur battery cells were cycled over 30 times and showedthe ability to reach 2.5 V at every cycle, demonstrating that thelithium oxysulfide layer performed well as a barrier, protecting lithiumfrom the polysulfide shuttle. Multiple cells autopsied after 10 chargecycles showed no defects in the lithium oxysulfide layer and showed noevidence of lithium metal deposition on top of the lithium oxysulfidelayer. All lithium was deposited under the lithium oxysulfide layer.Autopsies also showed that the ceramic and separator materials were wellbonded after cycling.

Comparative Example 2

This example shows the formation and performance of the ionconductor-separator composite of Comparative Example 1 in alithium-sulfur electrochemical cell.

Anodes with vacuum deposited lithium on the top of the ionconductor-separator composite of Comparative Example 1 were assembledinto lithium-sulfur battery cells and tested similarly as described inExample 2.

These cells were unable to be charged to 2.5 V over 30 cycles. Instead,charge time was at least 15 hours and charge voltage leveled at2.37-2.41 V. These results demonstrate that the lithium was notprotected from the polysulfide shuttle during cycling. Autopsy showedthat the lithium oxysulfide layer had defects and a substantial portionof lithium (˜20-30% of the surface area) was deposited on the top ofthis layer.

Example 3

This example demonstrates the ability of ion conductor-separatorcomposites (fabricated similarly to the method described in Example 1)to act as a barrier to fluids, as demonstrated by air permeation testing(Gurley test). Each of the samples included a 25 micron thick separatorwith pore diameters ranging between 0.1 micron to 0.5 microns, and acoating of lithium oxysulfide on top of the separator. Samples 1, 2, 3,and 6 included separators that were plasma treated before the additionof the lithium oxysulfide. Samples 4, 5, and 7 included separators thatwere untreated before the addition of the lithium oxysulfide layer.

FIG. 12 is a graph showing air permeation time versus ion conductorlayer thickness for composites including plasma treated and untreatedseparators. The figure highlights the improvement in air permeationtimes with plasma treatment of the separator before applying the lithiumoxysulfide coating, i.e., samples 1, 2, 3, and 6, compared to compositesthat included separators that were untreated before the addition of thelithium oxysulfide layer (samples 4, 5, and 7).

This example demonstrates that air permeation time generally increaseswhen the surface of the separator of the is subjected to plasmatreatment prior to deposition of the oxysulfide layer, which promotessufficient bonding between the oxysulfide layer and the separator. Theabsence of plasma treatment resulted in delamination of the oxysulfidelayer, and therefore leads to poorer barrier properties. This examplealso shows that the highest air permeation time (and, therefore,enhanced barrier properties) was achieved with a lithium oxysulfidelayer having a thickness of 0.5 microns (sample 1). This data suggeststhat thinner lithium oxysulfide layers generally lead to improvedbarrier properties compared to composites having thicker lithiumoxysulfide layers, with the combination of a thin lithium oxysulfidelayer and a plasma treated separator showing the highest air permeationtime (and, therefore, enhanced barrier properties).

While several embodiments of the present invention have been describedand illustrated herein, those of ordinary skill in the art will readilyenvision a variety of other means and/or structures for performing thefunctions and/or obtaining the results and/or one or more of theadvantages described herein, and each of such variations and/ormodifications is deemed to be within the scope of the present invention.More generally, those skilled in the art will readily appreciate thatall parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the teachings of thepresent invention is/are used. Those skilled in the art will recognize,or be able to ascertain using no more than routine experimentation, manyequivalents to the specific embodiments of the invention describedherein. It is, therefore, to be understood that the foregoingembodiments are presented by way of example only and that, within thescope of the appended claims and equivalents thereto, the invention maybe practiced otherwise than as specifically described and claimed. Thepresent invention is directed to each individual feature, system,article, material, and/or method described herein. In addition, anycombination of two or more such features, systems, articles, materials,and/or methods, if such features, systems, articles, materials, and/ormethods are not mutually inconsistent, is included within the scope ofthe present invention.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Other elements may optionallybe present other than the elements specifically identified by the“and/or” clause, whether related or unrelated to those elementsspecifically identified unless clearly indicated to the contrary. Thus,as a non-limiting example, a reference to “A and/or B,” when used inconjunction with open-ended language such as “comprising” can refer, inone embodiment, to A without B (optionally including elements other thanB); in another embodiment, to B without A (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of” or “exactly one of,” or, when usedin the claims, “consisting of,” will refer to the inclusion of exactlyone element of a number or list of elements. In general, the term “or”as used herein shall only be interpreted as indicating exclusivealternatives (i.e. “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of,” “only one of,” or“exactly one of.” “Consisting essentially of,” when used in the claims,shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” and the like are to be understoodto be open-ended, i.e., to mean including but not limited to. Only thetransitional phrases “consisting of” and “consisting essentially of”shall be closed or semi-closed transitional phrases, respectively, asset forth in the United States Patent Office Manual of Patent ExaminingProcedures, Section 2111.03.

What is claimed is:
 1. An electrochemical cell, comprising: a firstelectrode comprising an electroactive material, wherein the firstelectrode is a negative electrode; a second electrode; and a compositepositioned between the first and second electrodes, the compositecomprising: a separator comprising pores having an average pore size,wherein the separator has a bulk electronic resistivity of at least 10⁴Ohm-meters; and an inorganic ion conductor layer bonded to the separatorand positioned directly adjacent to the first electrode, wherein a ratioof a thickness of the inorganic ion conductor layer to the average poresize of the separator is at least 1.1:1, and wherein the composite hasan air permeation time of at least 20,000 Gurley-s and at most 200,000Gurley-s according to Gurley test TAPPI Standard T 536 om-12.
 2. Anelectrochemical cell, comprising: a first electrode comprising anelectroactive material, wherein the first electrode is a negativeelectrode; a second electrode; and a composite positioned between thefirst and second electrodes, the composite comprising: a separatorcomprising pores having an average pore size, wherein the separator hasa bulk electronic resistivity of at least 10⁴ Ohm-meters; and aninorganic ion conductor layer directly adjacent to the separator anddirectly adjacent to the first electrode, wherein the inorganic ionconductor layer has a thickness of less than or equal to 1.5 microns,and wherein the composite has an air permeation time of at least 20,000Gurley-s and at most 200,000 Gurley-s according to Gurley test TAPPIStandard T 536 om-12.
 3. An electrochemical cell, comprising: a firstelectrode comprising an electroactive material, wherein the firstelectrode is a negative electrode; a second electrode; and a compositepositioned between the first and second electrodes, the compositecomprising: a separator comprising pores having an average pore size,wherein the separator has a bulk electronic resistivity of at least 10⁴Ohm-meters; and an inorganic ion conductor layer bonded to theseparator, wherein the inorganic ion conductor layer is bonded to theseparator by covalent bonding, wherein the inorganic ion conductor layerhas an ion conductivity of least at least 10⁻⁷ S/cm, and wherein thecomposite has an air permeation time of at least 20,000 Gurley-s and atmost 200,000 Gurley-s according to Gurley test TAPPI Standard T 536om-12.
 4. An electrochemical cell of claim 1, wherein the inorganic ionconductor layer is bonded to the separator by covalent bonding.
 5. Anelectrochemical cell of claim 1, wherein the composite has an airpermeation time of at least 40,000 Gurley-s and at most 200,000Gurley-s.
 6. An electrochemical cell of claim 1, wherein the compositeis formed by subjecting a surface of the separator to a plasma and thendepositing the inorganic ion conductor layer on the surface of theseparator.
 7. An electrochemical cell of claim 1, wherein the separatorhas a thickness between 5 microns and 40 microns.
 8. An electrochemicalcell of claim 1, wherein the separator has a bulk electronic resistivityof at least 10¹⁰ Ohm-meters and/or less than or equal to 10¹⁵Ohm-meters.
 9. An electrochemical cell of claim 1, wherein the separatoris a solid, polymeric separator.
 10. An electrochemical cell of claim 1,wherein the separator comprises one or more of poly(n-pentene-2),polypropylene, polytetrafluoroethylene, a polyamide, and polyether etherketone (PEEK).
 11. An electrochemical cell of claim 1, wherein theinorganic ion conductor layer comprises an inorganic ion conductormaterial, and wherein the pores of the separator are substantiallyunfilled with the inorganic ion conductor material.
 12. Anelectrochemical cell of claim 1, wherein the inorganic ion conductorlayer comprises an inorganic ion conductor material, and wherein atleast a portion of the pores of the separator are filled with theinorganic ion conductor material.
 13. An electrochemical cell of claim1, wherein the average pore size of the separator is less than or equalto 5 microns.
 14. An electrochemical cell of claim 1, wherein theinorganic ion conductor layer has a thickness of less than or equal to 2microns.
 15. An electrochemical cell of claim 1, wherein the inorganicion conductor layer comprises a ceramic, a glass, and/or aglass-ceramic.
 16. An electrochemical cell of claim 1, wherein thecomposite has a lithium ion conductivity of at least 10⁻⁵ S/cm at 25degrees Celsius.
 17. An electrochemical cell of claim 1, wherein astrength of adhesion between the separator and the inorganic ionconductor layer is at least 350 N/m.
 18. An electrochemical cell ofclaim 1, wherein a strength of adhesion between the separator and theinorganic ion conductor layer passes the tape test according to thestandard ASTM D3359-02.
 19. An electrochemical cell of claim 1, whereinthe first electroactive material comprises lithium metal and/or alithium metal alloy.
 20. An electrochemical cell of claim 1, wherein thesecond electrode comprises sulfur as a second electroactive material.21. An electrochemical cell of claim 1, wherein the inorganic ionconductor layer comprises a metal oxide of the metal ion conductive inthe inorganic ion conductor layer.
 22. An electrochemical cell of claim1, wherein the inorganic ion conductor layer comprises one or more of alithium nitride, a lithium silicate, a lithium borate, a lithiumaluminate, a lithium phosphate, a lithium phosphorus oxynitride, alithium borosulfide, a lithium aluminosulfide, a lithium phosphosulfide,and a lithium oxysulfide.
 23. An electrochemical cell of claim 1,wherein the first electrode comprises lithium metal and/or a lithiummetal alloy, and wherein the inorganic ion conductor layer is conductiveto lithium ions.
 24. An electrochemical cell of claim 1, wherein theinorganic ion conductor layer serves as a solvent barrier.
 25. Anelectrochemical cell of claim 1, wherein the inorganic ion conductorlayer forms a smooth, dense, and homogeneous thin film.
 26. Anelectrochemical cell of claim 1, wherein the inorganic ion conductorlayer is a continuous layer.
 27. An electrochemical cell of claim 2,wherein the inorganic ion conductor layer functions as a protectivestructure within the electrochemical cell.
 28. An electrochemical cellof claim 3, wherein the inorganic ion conductor layer is positioneddirectly adjacent to the first electrode.
 29. An electrochemical cell ofclaim 1, wherein the electrochemical cell comprises an electrolyte, andwherein separator swells in the electrolyte.